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+/* ========================================================================== */
+/* === colamd - a sparse matrix column ordering algorithm =================== */
+/* ========================================================================== */
+
+/*
+ colamd: An approximate minimum degree column ordering algorithm.
+
+ Purpose:
+
+ Colamd computes a permutation Q such that the Cholesky factorization of
+ (AQ)'(AQ) has less fill-in and requires fewer floating point operations
+ than A'A. This also provides a good ordering for sparse partial
+ pivoting methods, P(AQ) = LU, where Q is computed prior to numerical
+ factorization, and P is computed during numerical factorization via
+ conventional partial pivoting with row interchanges. Colamd is the
+ column ordering method used in SuperLU, part of the ScaLAPACK library.
+ It is also available as user-contributed software for Matlab 5.2,
+ available from MathWorks, Inc. (http://www.mathworks.com). This
+ routine can be used in place of COLMMD in Matlab. By default, the \
+ and / operators in Matlab perform a column ordering (using COLMMD)
+ prior to LU factorization using sparse partial pivoting, in the
+ built-in Matlab LU(A) routine.
+
+ Authors:
+
+ The authors of the code itself are Stefan I. Larimore and Timothy A.
+ Davis (davis@cise.ufl.edu), University of Florida. The algorithm was
+ developed in collaboration with John Gilbert, Xerox PARC, and Esmond
+ Ng, Oak Ridge National Laboratory.
+
+ Date:
+
+ August 3, 1998. Version 1.0.
+
+ Acknowledgements:
+
+ This work was supported by the National Science Foundation, under
+ grants DMS-9504974 and DMS-9803599.
+
+ Notice:
+
+ Copyright (c) 1998 by the University of Florida. All Rights Reserved.
+
+ THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
+ EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
+
+ Permission is hereby granted to use or copy this program for any
+ purpose, provided the above notices are retained on all copies.
+ User documentation of any code that uses this code must cite the
+ Authors, the Copyright, and "Used by permission." If this code is
+ accessible from within Matlab, then typing "help colamd" or "colamd"
+ (with no arguments) must cite the Authors. Permission to modify the
+ code and to distribute modified code is granted, provided the above
+ notices are retained, and a notice that the code was modified is
+ included with the above copyright notice. You must also retain the
+ Availability information below, of the original version.
+
+ This software is provided free of charge.
+
+ Availability:
+
+ This file is located at
+
+ http://www.cise.ufl.edu/~davis/colamd/colamd.c
+
+ The colamd.h file is required, located in the same directory.
+ The colamdmex.c file provides a Matlab interface for colamd.
+ The symamdmex.c file provides a Matlab interface for symamd, which is
+ a symmetric ordering based on this code, colamd.c. All codes are
+ purely ANSI C compliant (they use no Unix-specific routines, include
+ files, etc.).
+*/
+
+/* ========================================================================== */
+/* === Description of user-callable routines ================================ */
+/* ========================================================================== */
+
+/*
+ Each user-callable routine (declared as PUBLIC) is briefly described below.
+ Refer to the comments preceding each routine for more details.
+
+ ----------------------------------------------------------------------------
+ colamd_recommended:
+ ----------------------------------------------------------------------------
+
+ Usage:
+
+ Alen = colamd_recommended (nnz, n_row, n_col) ;
+
+ Purpose:
+
+ Returns recommended value of Alen for use by colamd. Returns -1
+ if any input argument is negative.
+
+ Arguments:
+
+ int nnz ; Number of nonzeros in the matrix A. This must
+ be the same value as p [n_col] in the call to
+ colamd - otherwise you will get a wrong value
+ of the recommended memory to use.
+ int n_row ; Number of rows in the matrix A.
+ int n_col ; Number of columns in the matrix A.
+
+ ----------------------------------------------------------------------------
+ colamd_set_defaults:
+ ----------------------------------------------------------------------------
+
+ Usage:
+
+ colamd_set_defaults (knobs) ;
+
+ Purpose:
+
+ Sets the default parameters.
+
+ Arguments:
+
+ double knobs [COLAMD_KNOBS] ; Output only.
+
+ Rows with more than (knobs [COLAMD_DENSE_ROW] * n_col) entries
+ are removed prior to ordering. Columns with more than
+ (knobs [COLAMD_DENSE_COL] * n_row) entries are removed
+ prior to ordering, and placed last in the output column
+ ordering. Default values of these two knobs are both 0.5.
+ Currently, only knobs [0] and knobs [1] are used, but future
+ versions may use more knobs. If so, they will be properly set
+ to their defaults by the future version of colamd_set_defaults,
+ so that the code that calls colamd will not need to change,
+ assuming that you either use colamd_set_defaults, or pass a
+ (double *) NULL pointer as the knobs array to colamd.
+
+ ----------------------------------------------------------------------------
+ colamd:
+ ----------------------------------------------------------------------------
+
+ Usage:
+
+ colamd (n_row, n_col, Alen, A, p, knobs) ;
+
+ Purpose:
+
+ Computes a column ordering (Q) of A such that P(AQ)=LU or
+ (AQ)'AQ=LL' have less fill-in and require fewer floating point
+ operations than factorizing the unpermuted matrix A or A'A,
+ respectively.
+
+ Arguments:
+
+ int n_row ;
+
+ Number of rows in the matrix A.
+ Restriction: n_row >= 0.
+ Colamd returns FALSE if n_row is negative.
+
+ int n_col ;
+
+ Number of columns in the matrix A.
+ Restriction: n_col >= 0.
+ Colamd returns FALSE if n_col is negative.
+
+ int Alen ;
+
+ Restriction (see note):
+ Alen >= 2*nnz + 6*(n_col+1) + 4*(n_row+1) + n_col + COLAMD_STATS
+ Colamd returns FALSE if these conditions are not met.
+
+ Note: this restriction makes an modest assumption regarding
+ the size of the two typedef'd structures, below. We do,
+ however, guarantee that
+ Alen >= colamd_recommended (nnz, n_row, n_col)
+ will be sufficient.
+
+ int A [Alen] ; Input argument, stats on output.
+
+ A is an integer array of size Alen. Alen must be at least as
+ large as the bare minimum value given above, but this is very
+ low, and can result in excessive run time. For best
+ performance, we recommend that Alen be greater than or equal to
+ colamd_recommended (nnz, n_row, n_col), which adds
+ nnz/5 to the bare minimum value given above.
+
+ On input, the row indices of the entries in column c of the
+ matrix are held in A [(p [c]) ... (p [c+1]-1)]. The row indices
+ in a given column c need not be in ascending order, and
+ duplicate row indices may be be present. However, colamd will
+ work a little faster if both of these conditions are met
+ (Colamd puts the matrix into this format, if it finds that the
+ the conditions are not met).
+
+ The matrix is 0-based. That is, rows are in the range 0 to
+ n_row-1, and columns are in the range 0 to n_col-1. Colamd
+ returns FALSE if any row index is out of range.
+
+ The contents of A are modified during ordering, and are thus
+ undefined on output with the exception of a few statistics
+ about the ordering (A [0..COLAMD_STATS-1]):
+ A [0]: number of dense or empty rows ignored.
+ A [1]: number of dense or empty columns ignored (and ordered
+ last in the output permutation p)
+ A [2]: number of garbage collections performed.
+ A [3]: 0, if all row indices in each column were in sorted
+ order, and no duplicates were present.
+ 1, otherwise (in which case colamd had to do more work)
+ Note that a row can become "empty" if it contains only
+ "dense" and/or "empty" columns, and similarly a column can
+ become "empty" if it only contains "dense" and/or "empty" rows.
+ Future versions may return more statistics in A, but the usage
+ of these 4 entries in A will remain unchanged.
+
+ int p [n_col+1] ; Both input and output argument.
+
+ p is an integer array of size n_col+1. On input, it holds the
+ "pointers" for the column form of the matrix A. Column c of
+ the matrix A is held in A [(p [c]) ... (p [c+1]-1)]. The first
+ entry, p [0], must be zero, and p [c] <= p [c+1] must hold
+ for all c in the range 0 to n_col-1. The value p [n_col] is
+ thus the total number of entries in the pattern of the matrix A.
+ Colamd returns FALSE if these conditions are not met.
+
+ On output, if colamd returns TRUE, the array p holds the column
+ permutation (Q, for P(AQ)=LU or (AQ)'(AQ)=LL'), where p [0] is
+ the first column index in the new ordering, and p [n_col-1] is
+ the last. That is, p [k] = j means that column j of A is the
+ kth pivot column, in AQ, where k is in the range 0 to n_col-1
+ (p [0] = j means that column j of A is the first column in AQ).
+
+ If colamd returns FALSE, then no permutation is returned, and
+ p is undefined on output.
+
+ double knobs [COLAMD_KNOBS] ; Input only.
+
+ See colamd_set_defaults for a description. If the knobs array
+ is not present (that is, if a (double *) NULL pointer is passed
+ in its place), then the default values of the parameters are
+ used instead.
+
+*/
+
+
+/* ========================================================================== */
+/* === Include files ======================================================== */
+/* ========================================================================== */
+
+/* limits.h: the largest positive integer (INT_MAX) */
+#include <limits.h>
+
+/* colamd.h: knob array size, stats output size, and global prototypes */
+#include "colamd.h"
+
+/* ========================================================================== */
+/* === Scaffolding code definitions ======================================== */
+/* ========================================================================== */
+
+/* Ensure that debugging is turned off: */
+#ifndef NDEBUG
+#define NDEBUG
+#endif
+
+/* assert.h: the assert macro (no debugging if NDEBUG is defined) */
+#include <assert.h>
+
+/*
+ Our "scaffolding code" philosophy: In our opinion, well-written library
+ code should keep its "debugging" code, and just normally have it turned off
+ by the compiler so as not to interfere with performance. This serves
+ several purposes:
+
+ (1) assertions act as comments to the reader, telling you what the code
+ expects at that point. All assertions will always be true (unless
+ there really is a bug, of course).
+
+ (2) leaving in the scaffolding code assists anyone who would like to modify
+ the code, or understand the algorithm (by reading the debugging output,
+ one can get a glimpse into what the code is doing).
+
+ (3) (gasp!) for actually finding bugs. This code has been heavily tested
+ and "should" be fully functional and bug-free ... but you never know...
+
+ To enable debugging, comment out the "#define NDEBUG" above. The code will
+ become outrageously slow when debugging is enabled. To control the level of
+ debugging output, set an environment variable D to 0 (little), 1 (some),
+ 2, 3, or 4 (lots).
+*/
+
+/* ========================================================================== */
+/* === Row and Column structures ============================================ */
+/* ========================================================================== */
+
+typedef struct ColInfo_struct
+{
+ int start ; /* index for A of first row in this column, or DEAD */
+ /* if column is dead */
+ int length ; /* number of rows in this column */
+ union
+ {
+ int thickness ; /* number of original columns represented by this */
+ /* col, if the column is alive */
+ int parent ; /* parent in parent tree super-column structure, if */
+ /* the column is dead */
+ } shared1 ;
+ union
+ {
+ int score ; /* the score used to maintain heap, if col is alive */
+ int order ; /* pivot ordering of this column, if col is dead */
+ } shared2 ;
+ union
+ {
+ int headhash ; /* head of a hash bucket, if col is at the head of */
+ /* a degree list */
+ int hash ; /* hash value, if col is not in a degree list */
+ int prev ; /* previous column in degree list, if col is in a */
+ /* degree list (but not at the head of a degree list) */
+ } shared3 ;
+ union
+ {
+ int degree_next ; /* next column, if col is in a degree list */
+ int hash_next ; /* next column, if col is in a hash list */
+ } shared4 ;
+
+} ColInfo ;
+
+typedef struct RowInfo_struct
+{
+ int start ; /* index for A of first col in this row */
+ int length ; /* number of principal columns in this row */
+ union
+ {
+ int degree ; /* number of principal & non-principal columns in row */
+ int p ; /* used as a row pointer in init_rows_cols () */
+ } shared1 ;
+ union
+ {
+ int mark ; /* for computing set differences and marking dead rows*/
+ int first_column ;/* first column in row (used in garbage collection) */
+ } shared2 ;
+
+} RowInfo ;
+
+/* ========================================================================== */
+/* === Definitions ========================================================== */
+/* ========================================================================== */
+
+#define MAX(a,b) (((a) > (b)) ? (a) : (b))
+#define MIN(a,b) (((a) < (b)) ? (a) : (b))
+
+#define ONES_COMPLEMENT(r) (-(r)-1)
+
+#define TRUE (1)
+#define FALSE (0)
+#define EMPTY (-1)
+
+/* Row and column status */
+#define ALIVE (0)
+#define DEAD (-1)
+
+/* Column status */
+#define DEAD_PRINCIPAL (-1)
+#define DEAD_NON_PRINCIPAL (-2)
+
+/* Macros for row and column status update and checking. */
+#define ROW_IS_DEAD(r) ROW_IS_MARKED_DEAD (Row[r].shared2.mark)
+#define ROW_IS_MARKED_DEAD(row_mark) (row_mark < ALIVE)
+#define ROW_IS_ALIVE(r) (Row [r].shared2.mark >= ALIVE)
+#define COL_IS_DEAD(c) (Col [c].start < ALIVE)
+#define COL_IS_ALIVE(c) (Col [c].start >= ALIVE)
+#define COL_IS_DEAD_PRINCIPAL(c) (Col [c].start == DEAD_PRINCIPAL)
+#define KILL_ROW(r) { Row [r].shared2.mark = DEAD ; }
+#define KILL_PRINCIPAL_COL(c) { Col [c].start = DEAD_PRINCIPAL ; }
+#define KILL_NON_PRINCIPAL_COL(c) { Col [c].start = DEAD_NON_PRINCIPAL ; }
+
+/* Routines are either PUBLIC (user-callable) or PRIVATE (not user-callable) */
+#define PUBLIC
+#define PRIVATE static
+
+/* ========================================================================== */
+/* === Prototypes of PRIVATE routines ======================================= */
+/* ========================================================================== */
+
+PRIVATE int init_rows_cols
+(
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int A [],
+ int p []
+) ;
+
+PRIVATE void init_scoring
+(
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int A [],
+ int head [],
+ double knobs [COLAMD_KNOBS],
+ int *p_n_row2,
+ int *p_n_col2,
+ int *p_max_deg
+) ;
+
+PRIVATE int find_ordering
+(
+ int n_row,
+ int n_col,
+ int Alen,
+ RowInfo Row [],
+ ColInfo Col [],
+ int A [],
+ int head [],
+ int n_col2,
+ int max_deg,
+ int pfree
+) ;
+
+PRIVATE void order_children
+(
+ int n_col,
+ ColInfo Col [],
+ int p []
+) ;
+
+PRIVATE void detect_super_cols
+(
+#ifndef NDEBUG
+ int n_col,
+ RowInfo Row [],
+#endif
+ ColInfo Col [],
+ int A [],
+ int head [],
+ int row_start,
+ int row_length
+) ;
+
+PRIVATE int garbage_collection
+(
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int A [],
+ int *pfree
+) ;
+
+PRIVATE int clear_mark
+(
+ int n_row,
+ RowInfo Row []
+) ;
+
+/* ========================================================================== */
+/* === Debugging definitions ================================================ */
+/* ========================================================================== */
+
+#ifndef NDEBUG
+
+/* === With debugging ======================================================= */
+
+/* stdlib.h: for getenv and atoi, to get debugging level from environment */
+#include <stdlib.h>
+
+/* stdio.h: for printf (no printing if debugging is turned off) */
+#include <stdio.h>
+
+PRIVATE void debug_deg_lists
+(
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int head [],
+ int min_score,
+ int should,
+ int max_deg
+) ;
+
+PRIVATE void debug_mark
+(
+ int n_row,
+ RowInfo Row [],
+ int tag_mark,
+ int max_mark
+) ;
+
+PRIVATE void debug_matrix
+(
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int A []
+) ;
+
+PRIVATE void debug_structures
+(
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int A [],
+ int n_col2
+) ;
+
+/* the following is the *ONLY* global variable in this file, and is only */
+/* present when debugging */
+
+PRIVATE int debug_colamd ; /* debug print level */
+
+#define DEBUG0(params) { (void) printf params ; }
+#define DEBUG1(params) { if (debug_colamd >= 1) (void) printf params ; }
+#define DEBUG2(params) { if (debug_colamd >= 2) (void) printf params ; }
+#define DEBUG3(params) { if (debug_colamd >= 3) (void) printf params ; }
+#define DEBUG4(params) { if (debug_colamd >= 4) (void) printf params ; }
+
+#else
+
+/* === No debugging ========================================================= */
+
+#define DEBUG0(params) ;
+#define DEBUG1(params) ;
+#define DEBUG2(params) ;
+#define DEBUG3(params) ;
+#define DEBUG4(params) ;
+
+#endif
+
+/* ========================================================================== */
+
+
+/* ========================================================================== */
+/* === USER-CALLABLE ROUTINES: ============================================== */
+/* ========================================================================== */
+
+
+/* ========================================================================== */
+/* === colamd_recommended =================================================== */
+/* ========================================================================== */
+
+/*
+ The colamd_recommended routine returns the suggested size for Alen. This
+ value has been determined to provide good balance between the number of
+ garbage collections and the memory requirements for colamd.
+*/
+
+PUBLIC int colamd_recommended /* returns recommended value of Alen. */
+(
+ /* === Parameters ======================================================= */
+
+ int nnz, /* number of nonzeros in A */
+ int n_row, /* number of rows in A */
+ int n_col /* number of columns in A */
+)
+{
+ /* === Local variables ================================================== */
+
+ int minimum ; /* bare minimum requirements */
+ int recommended ; /* recommended value of Alen */
+
+ if (nnz < 0 || n_row < 0 || n_col < 0)
+ {
+ /* return -1 if any input argument is corrupted */
+ DEBUG0 (("colamd_recommended error!")) ;
+ DEBUG0 ((" nnz: %d, n_row: %d, n_col: %d\n", nnz, n_row, n_col)) ;
+ return (-1) ;
+ }
+
+ minimum =
+ 2 * (nnz) /* for A */
+ + (((n_col) + 1) * sizeof (ColInfo) / sizeof (int)) /* for Col */
+ + (((n_row) + 1) * sizeof (RowInfo) / sizeof (int)) /* for Row */
+ + n_col /* minimum elbow room to guarrantee success */
+ + COLAMD_STATS ; /* for output statistics */
+
+ /* recommended is equal to the minumum plus enough memory to keep the */
+ /* number garbage collections low */
+ recommended = minimum + nnz/5 ;
+
+ return (recommended) ;
+}
+
+
+/* ========================================================================== */
+/* === colamd_set_defaults ================================================== */
+/* ========================================================================== */
+
+/*
+ The colamd_set_defaults routine sets the default values of the user-
+ controllable parameters for colamd:
+
+ knobs [0] rows with knobs[0]*n_col entries or more are removed
+ prior to ordering.
+
+ knobs [1] columns with knobs[1]*n_row entries or more are removed
+ prior to ordering, and placed last in the column
+ permutation.
+
+ knobs [2..19] unused, but future versions might use this
+*/
+
+PUBLIC void colamd_set_defaults
+(
+ /* === Parameters ======================================================= */
+
+ double knobs [COLAMD_KNOBS] /* knob array */
+)
+{
+ /* === Local variables ================================================== */
+
+ int i ;
+
+ if (!knobs)
+ {
+ return ; /* no knobs to initialize */
+ }
+ for (i = 0 ; i < COLAMD_KNOBS ; i++)
+ {
+ knobs [i] = 0 ;
+ }
+ knobs [COLAMD_DENSE_ROW] = 0.5 ; /* ignore rows over 50% dense */
+ knobs [COLAMD_DENSE_COL] = 0.5 ; /* ignore columns over 50% dense */
+}
+
+
+/* ========================================================================== */
+/* === colamd =============================================================== */
+/* ========================================================================== */
+
+/*
+ The colamd routine computes a column ordering Q of a sparse matrix
+ A such that the LU factorization P(AQ) = LU remains sparse, where P is
+ selected via partial pivoting. The routine can also be viewed as
+ providing a permutation Q such that the Cholesky factorization
+ (AQ)'(AQ) = LL' remains sparse.
+
+ On input, the nonzero patterns of the columns of A are stored in the
+ array A, in order 0 to n_col-1. A is held in 0-based form (rows in the
+ range 0 to n_row-1 and columns in the range 0 to n_col-1). Row indices
+ for column c are located in A [(p [c]) ... (p [c+1]-1)], where p [0] = 0,
+ and thus p [n_col] is the number of entries in A. The matrix is
+ destroyed on output. The row indices within each column do not have to
+ be sorted (from small to large row indices), and duplicate row indices
+ may be present. However, colamd will work a little faster if columns are
+ sorted and no duplicates are present. Matlab 5.2 always passes the matrix
+ with sorted columns, and no duplicates.
+
+ The integer array A is of size Alen. Alen must be at least of size
+ (where nnz is the number of entries in A):
+
+ nnz for the input column form of A
+ + nnz for a row form of A that colamd generates
+ + 6*(n_col+1) for a ColInfo Col [0..n_col] array
+ (this assumes sizeof (ColInfo) is 6 int's).
+ + 4*(n_row+1) for a RowInfo Row [0..n_row] array
+ (this assumes sizeof (RowInfo) is 4 int's).
+ + elbow_room must be at least n_col. We recommend at least
+ nnz/5 in addition to that. If sufficient,
+ changes in the elbow room affect the ordering
+ time only, not the ordering itself.
+ + COLAMD_STATS for the output statistics
+
+ Colamd returns FALSE is memory is insufficient, or TRUE otherwise.
+
+ On input, the caller must specify:
+
+ n_row the number of rows of A
+ n_col the number of columns of A
+ Alen the size of the array A
+ A [0 ... nnz-1] the row indices, where nnz = p [n_col]
+ A [nnz ... Alen-1] (need not be initialized by the user)
+ p [0 ... n_col] the column pointers, p [0] = 0, and p [n_col]
+ is the number of entries in A. Column c of A
+ is stored in A [p [c] ... p [c+1]-1].
+ knobs [0 ... 19] a set of parameters that control the behavior
+ of colamd. If knobs is a NULL pointer the
+ defaults are used. The user-callable
+ colamd_set_defaults routine sets the default
+ parameters. See that routine for a description
+ of the user-controllable parameters.
+
+ If the return value of Colamd is TRUE, then on output:
+
+ p [0 ... n_col-1] the column permutation. p [0] is the first
+ column index, and p [n_col-1] is the last.
+ That is, p [k] = j means that column j of A
+ is the kth column of AQ.
+
+ A is undefined on output (the matrix pattern is
+ destroyed), except for the following statistics:
+
+ A [0] the number of dense (or empty) rows ignored
+ A [1] the number of dense (or empty) columms. These
+ are ordered last, in their natural order.
+ A [2] the number of garbage collections performed.
+ If this is excessive, then you would have
+ gotten your results faster if Alen was larger.
+ A [3] 0, if all row indices in each column were in
+ sorted order and no duplicates were present.
+ 1, if there were unsorted or duplicate row
+ indices in the input. You would have gotten
+ your results faster if A [3] was returned as 0.
+
+ If the return value of Colamd is FALSE, then A and p are undefined on
+ output.
+*/
+
+PUBLIC int colamd /* returns TRUE if successful */
+(
+ /* === Parameters ======================================================= */
+
+ int n_row, /* number of rows in A */
+ int n_col, /* number of columns in A */
+ int Alen, /* length of A */
+ int A [], /* row indices of A */
+ int p [], /* pointers to columns in A */
+ double knobs [COLAMD_KNOBS] /* parameters (uses defaults if NULL) */
+)
+{
+ /* === Local variables ================================================== */
+
+ int i ; /* loop index */
+ int nnz ; /* nonzeros in A */
+ int Row_size ; /* size of Row [], in integers */
+ int Col_size ; /* size of Col [], in integers */
+ int elbow_room ; /* remaining free space */
+ RowInfo *Row ; /* pointer into A of Row [0..n_row] array */
+ ColInfo *Col ; /* pointer into A of Col [0..n_col] array */
+ int n_col2 ; /* number of non-dense, non-empty columns */
+ int n_row2 ; /* number of non-dense, non-empty rows */
+ int ngarbage ; /* number of garbage collections performed */
+ int max_deg ; /* maximum row degree */
+ double default_knobs [COLAMD_KNOBS] ; /* default knobs knobs array */
+ int init_result ; /* return code from initialization */
+
+#ifndef NDEBUG
+ debug_colamd = 0 ; /* no debug printing */
+ /* get "D" environment variable, which gives the debug printing level */
+ if (getenv ("D")) debug_colamd = atoi (getenv ("D")) ;
+ DEBUG0 (("debug version, D = %d (THIS WILL BE SLOOOOW!)\n", debug_colamd)) ;
+#endif
+
+ /* === Check the input arguments ======================================== */
+
+ if (n_row < 0 || n_col < 0 || !A || !p)
+ {
+ /* n_row and n_col must be non-negative, A and p must be present */
+ DEBUG0 (("colamd error! %d %d %d\n", n_row, n_col, Alen)) ;
+ return (FALSE) ;
+ }
+ nnz = p [n_col] ;
+ if (nnz < 0 || p [0] != 0)
+ {
+ /* nnz must be non-negative, and p [0] must be zero */
+ DEBUG0 (("colamd error! %d %d\n", nnz, p [0])) ;
+ return (FALSE) ;
+ }
+
+ /* === If no knobs, set default parameters ============================== */
+
+ if (!knobs)
+ {
+ knobs = default_knobs ;
+ colamd_set_defaults (knobs) ;
+ }
+
+ /* === Allocate the Row and Col arrays from array A ===================== */
+
+ Col_size = (n_col + 1) * sizeof (ColInfo) / sizeof (int) ;
+ Row_size = (n_row + 1) * sizeof (RowInfo) / sizeof (int) ;
+ elbow_room = Alen - (2*nnz + Col_size + Row_size) ;
+ if (elbow_room < n_col + COLAMD_STATS)
+ {
+ /* not enough space in array A to perform the ordering */
+ DEBUG0 (("colamd error! elbow_room %d, %d\n", elbow_room,n_col)) ;
+ return (FALSE) ;
+ }
+ Alen = 2*nnz + elbow_room ;
+ Col = (ColInfo *) &A [Alen] ;
+ Row = (RowInfo *) &A [Alen + Col_size] ;
+
+ /* === Construct the row and column data structures ===================== */
+
+ init_result = init_rows_cols (n_row, n_col, Row, Col, A, p) ;
+ if (init_result == -1)
+ {
+ /* input matrix is invalid */
+ DEBUG0 (("colamd error! matrix invalid\n")) ;
+ return (FALSE) ;
+ }
+
+ /* === Initialize scores, kill dense rows/columns ======================= */
+
+ init_scoring (n_row, n_col, Row, Col, A, p, knobs,
+ &n_row2, &n_col2, &max_deg) ;
+
+ /* === Order the supercolumns =========================================== */
+
+ ngarbage = find_ordering (n_row, n_col, Alen, Row, Col, A, p,
+ n_col2, max_deg, 2*nnz) ;
+
+ /* === Order the non-principal columns ================================== */
+
+ order_children (n_col, Col, p) ;
+
+ /* === Return statistics in A =========================================== */
+
+ for (i = 0 ; i < COLAMD_STATS ; i++)
+ {
+ A [i] = 0 ;
+ }
+ A [COLAMD_DENSE_ROW] = n_row - n_row2 ;
+ A [COLAMD_DENSE_COL] = n_col - n_col2 ;
+ A [COLAMD_DEFRAG_COUNT] = ngarbage ;
+ A [COLAMD_JUMBLED_COLS] = init_result ;
+
+ return (TRUE) ;
+}
+
+
+/* ========================================================================== */
+/* === NON-USER-CALLABLE ROUTINES: ========================================== */
+/* ========================================================================== */
+
+/* There are no user-callable routines beyond this point in the file */
+
+
+/* ========================================================================== */
+/* === init_rows_cols ======================================================= */
+/* ========================================================================== */
+
+/*
+ Takes the column form of the matrix in A and creates the row form of the
+ matrix. Also, row and column attributes are stored in the Col and Row
+ structs. If the columns are un-sorted or contain duplicate row indices,
+ this routine will also sort and remove duplicate row indices from the
+ column form of the matrix. Returns -1 on error, 1 if columns jumbled,
+ or 0 if columns not jumbled. Not user-callable.
+*/
+
+PRIVATE int init_rows_cols /* returns status code */
+(
+ /* === Parameters ======================================================= */
+
+ int n_row, /* number of rows of A */
+ int n_col, /* number of columns of A */
+ RowInfo Row [], /* of size n_row+1 */
+ ColInfo Col [], /* of size n_col+1 */
+ int A [], /* row indices of A, of size Alen */
+ int p [] /* pointers to columns in A, of size n_col+1 */
+)
+{
+ /* === Local variables ================================================== */
+
+ int col ; /* a column index */
+ int row ; /* a row index */
+ int *cp ; /* a column pointer */
+ int *cp_end ; /* a pointer to the end of a column */
+ int *rp ; /* a row pointer */
+ int *rp_end ; /* a pointer to the end of a row */
+ int last_start ; /* start index of previous column in A */
+ int start ; /* start index of column in A */
+ int last_row ; /* previous row */
+ int jumbled_columns ; /* indicates if columns are jumbled */
+
+ /* === Initialize columns, and check column pointers ==================== */
+
+ last_start = 0 ;
+ for (col = 0 ; col < n_col ; col++)
+ {
+ start = p [col] ;
+ if (start < last_start)
+ {
+ /* column pointers must be non-decreasing */
+ DEBUG0 (("colamd error! last p %d p [col] %d\n",last_start,start));
+ return (-1) ;
+ }
+ Col [col].start = start ;
+ Col [col].length = p [col+1] - start ;
+ Col [col].shared1.thickness = 1 ;
+ Col [col].shared2.score = 0 ;
+ Col [col].shared3.prev = EMPTY ;
+ Col [col].shared4.degree_next = EMPTY ;
+ last_start = start ;
+ }
+ /* must check the end pointer for last column */
+ if (p [n_col] < last_start)
+ {
+ /* column pointers must be non-decreasing */
+ DEBUG0 (("colamd error! last p %d p [n_col] %d\n",p[col],last_start)) ;
+ return (-1) ;
+ }
+
+ /* p [0..n_col] no longer needed, used as "head" in subsequent routines */
+
+ /* === Scan columns, compute row degrees, and check row indices ========= */
+
+ jumbled_columns = FALSE ;
+
+ for (row = 0 ; row < n_row ; row++)
+ {
+ Row [row].length = 0 ;
+ Row [row].shared2.mark = -1 ;
+ }
+
+ for (col = 0 ; col < n_col ; col++)
+ {
+ last_row = -1 ;
+
+ cp = &A [p [col]] ;
+ cp_end = &A [p [col+1]] ;
+
+ while (cp < cp_end)
+ {
+ row = *cp++ ;
+
+ /* make sure row indices within range */
+ if (row < 0 || row >= n_row)
+ {
+ DEBUG0 (("colamd error! col %d row %d last_row %d\n",
+ col, row, last_row)) ;
+ return (-1) ;
+ }
+ else if (row <= last_row)
+ {
+ /* row indices are not sorted or repeated, thus cols */
+ /* are jumbled */
+ jumbled_columns = TRUE ;
+ }
+ /* prevent repeated row from being counted */
+ if (Row [row].shared2.mark != col)
+ {
+ Row [row].length++ ;
+ Row [row].shared2.mark = col ;
+ last_row = row ;
+ }
+ else
+ {
+ /* this is a repeated entry in the column, */
+ /* it will be removed */
+ Col [col].length-- ;
+ }
+ }
+ }
+
+ /* === Compute row pointers ============================================= */
+
+ /* row form of the matrix starts directly after the column */
+ /* form of matrix in A */
+ Row [0].start = p [n_col] ;
+ Row [0].shared1.p = Row [0].start ;
+ Row [0].shared2.mark = -1 ;
+ for (row = 1 ; row < n_row ; row++)
+ {
+ Row [row].start = Row [row-1].start + Row [row-1].length ;
+ Row [row].shared1.p = Row [row].start ;
+ Row [row].shared2.mark = -1 ;
+ }
+
+ /* === Create row form ================================================== */
+
+ if (jumbled_columns)
+ {
+ /* if cols jumbled, watch for repeated row indices */
+ for (col = 0 ; col < n_col ; col++)
+ {
+ cp = &A [p [col]] ;
+ cp_end = &A [p [col+1]] ;
+ while (cp < cp_end)
+ {
+ row = *cp++ ;
+ if (Row [row].shared2.mark != col)
+ {
+ A [(Row [row].shared1.p)++] = col ;
+ Row [row].shared2.mark = col ;
+ }
+ }
+ }
+ }
+ else
+ {
+ /* if cols not jumbled, we don't need the mark (this is faster) */
+ for (col = 0 ; col < n_col ; col++)
+ {
+ cp = &A [p [col]] ;
+ cp_end = &A [p [col+1]] ;
+ while (cp < cp_end)
+ {
+ A [(Row [*cp++].shared1.p)++] = col ;
+ }
+ }
+ }
+
+ /* === Clear the row marks and set row degrees ========================== */
+
+ for (row = 0 ; row < n_row ; row++)
+ {
+ Row [row].shared2.mark = 0 ;
+ Row [row].shared1.degree = Row [row].length ;
+ }
+
+ /* === See if we need to re-create columns ============================== */
+
+ if (jumbled_columns)
+ {
+
+#ifndef NDEBUG
+ /* make sure column lengths are correct */
+ for (col = 0 ; col < n_col ; col++)
+ {
+ p [col] = Col [col].length ;
+ }
+ for (row = 0 ; row < n_row ; row++)
+ {
+ rp = &A [Row [row].start] ;
+ rp_end = rp + Row [row].length ;
+ while (rp < rp_end)
+ {
+ p [*rp++]-- ;
+ }
+ }
+ for (col = 0 ; col < n_col ; col++)
+ {
+ assert (p [col] == 0) ;
+ }
+ /* now p is all zero (different than when debugging is turned off) */
+#endif
+
+ /* === Compute col pointers ========================================= */
+
+ /* col form of the matrix starts at A [0]. */
+ /* Note, we may have a gap between the col form and the row */
+ /* form if there were duplicate entries, if so, it will be */
+ /* removed upon the first garbage collection */
+ Col [0].start = 0 ;
+ p [0] = Col [0].start ;
+ for (col = 1 ; col < n_col ; col++)
+ {
+ /* note that the lengths here are for pruned columns, i.e. */
+ /* no duplicate row indices will exist for these columns */
+ Col [col].start = Col [col-1].start + Col [col-1].length ;
+ p [col] = Col [col].start ;
+ }
+
+ /* === Re-create col form =========================================== */
+
+ for (row = 0 ; row < n_row ; row++)
+ {
+ rp = &A [Row [row].start] ;
+ rp_end = rp + Row [row].length ;
+ while (rp < rp_end)
+ {
+ A [(p [*rp++])++] = row ;
+ }
+ }
+ return (1) ;
+ }
+ else
+ {
+ /* no columns jumbled (this is faster) */
+ return (0) ;
+ }
+}
+
+
+/* ========================================================================== */
+/* === init_scoring ========================================================= */
+/* ========================================================================== */
+
+/*
+ Kills dense or empty columns and rows, calculates an initial score for
+ each column, and places all columns in the degree lists. Not user-callable.
+*/
+
+PRIVATE void init_scoring
+(
+ /* === Parameters ======================================================= */
+
+ int n_row, /* number of rows of A */
+ int n_col, /* number of columns of A */
+ RowInfo Row [], /* of size n_row+1 */
+ ColInfo Col [], /* of size n_col+1 */
+ int A [], /* column form and row form of A */
+ int head [], /* of size n_col+1 */
+ double knobs [COLAMD_KNOBS],/* parameters */
+ int *p_n_row2, /* number of non-dense, non-empty rows */
+ int *p_n_col2, /* number of non-dense, non-empty columns */
+ int *p_max_deg /* maximum row degree */
+)
+{
+ /* === Local variables ================================================== */
+
+ int c ; /* a column index */
+ int r, row ; /* a row index */
+ int *cp ; /* a column pointer */
+ int deg ; /* degree (# entries) of a row or column */
+ int *cp_end ; /* a pointer to the end of a column */
+ int *new_cp ; /* new column pointer */
+ int col_length ; /* length of pruned column */
+ int score ; /* current column score */
+ int n_col2 ; /* number of non-dense, non-empty columns */
+ int n_row2 ; /* number of non-dense, non-empty rows */
+ int dense_row_count ; /* remove rows with more entries than this */
+ int dense_col_count ; /* remove cols with more entries than this */
+ int min_score ; /* smallest column score */
+ int max_deg ; /* maximum row degree */
+ int next_col ; /* Used to add to degree list.*/
+#ifndef NDEBUG
+ int debug_count ; /* debug only. */
+#endif
+
+ /* === Extract knobs ==================================================== */
+
+ dense_row_count = MAX (0, MIN (knobs [COLAMD_DENSE_ROW] * n_col, n_col)) ;
+ dense_col_count = MAX (0, MIN (knobs [COLAMD_DENSE_COL] * n_row, n_row)) ;
+ DEBUG0 (("densecount: %d %d\n", dense_row_count, dense_col_count)) ;
+ max_deg = 0 ;
+ n_col2 = n_col ;
+ n_row2 = n_row ;
+
+ /* === Kill empty columns =============================================== */
+
+ /* Put the empty columns at the end in their natural, so that LU */
+ /* factorization can proceed as far as possible. */
+ for (c = n_col-1 ; c >= 0 ; c--)
+ {
+ deg = Col [c].length ;
+ if (deg == 0)
+ {
+ /* this is a empty column, kill and order it last */
+ Col [c].shared2.order = --n_col2 ;
+ KILL_PRINCIPAL_COL (c) ;
+ }
+ }
+ DEBUG0 (("null columns killed: %d\n", n_col - n_col2)) ;
+
+ /* === Kill dense columns =============================================== */
+
+ /* Put the dense columns at the end, in their natural order */
+ for (c = n_col-1 ; c >= 0 ; c--)
+ {
+ /* skip any dead columns */
+ if (COL_IS_DEAD (c))
+ {
+ continue ;
+ }
+ deg = Col [c].length ;
+ if (deg > dense_col_count)
+ {
+ /* this is a dense column, kill and order it last */
+ Col [c].shared2.order = --n_col2 ;
+ /* decrement the row degrees */
+ cp = &A [Col [c].start] ;
+ cp_end = cp + Col [c].length ;
+ while (cp < cp_end)
+ {
+ Row [*cp++].shared1.degree-- ;
+ }
+ KILL_PRINCIPAL_COL (c) ;
+ }
+ }
+ DEBUG0 (("Dense and null columns killed: %d\n", n_col - n_col2)) ;
+
+ /* === Kill dense and empty rows ======================================== */
+
+ for (r = 0 ; r < n_row ; r++)
+ {
+ deg = Row [r].shared1.degree ;
+ assert (deg >= 0 && deg <= n_col) ;
+ if (deg > dense_row_count || deg == 0)
+ {
+ /* kill a dense or empty row */
+ KILL_ROW (r) ;
+ --n_row2 ;
+ }
+ else
+ {
+ /* keep track of max degree of remaining rows */
+ max_deg = MAX (max_deg, deg) ;
+ }
+ }
+ DEBUG0 (("Dense and null rows killed: %d\n", n_row - n_row2)) ;
+
+ /* === Compute initial column scores ==================================== */
+
+ /* At this point the row degrees are accurate. They reflect the number */
+ /* of "live" (non-dense) columns in each row. No empty rows exist. */
+ /* Some "live" columns may contain only dead rows, however. These are */
+ /* pruned in the code below. */
+
+ /* now find the initial matlab score for each column */
+ for (c = n_col-1 ; c >= 0 ; c--)
+ {
+ /* skip dead column */
+ if (COL_IS_DEAD (c))
+ {
+ continue ;
+ }
+ score = 0 ;
+ cp = &A [Col [c].start] ;
+ new_cp = cp ;
+ cp_end = cp + Col [c].length ;
+ while (cp < cp_end)
+ {
+ /* get a row */
+ row = *cp++ ;
+ /* skip if dead */
+ if (ROW_IS_DEAD (row))
+ {
+ continue ;
+ }
+ /* compact the column */
+ *new_cp++ = row ;
+ /* add row's external degree */
+ score += Row [row].shared1.degree - 1 ;
+ /* guard against integer overflow */
+ score = MIN (score, n_col) ;
+ }
+ /* determine pruned column length */
+ col_length = (int) (new_cp - &A [Col [c].start]) ;
+ if (col_length == 0)
+ {
+ /* a newly-made null column (all rows in this col are "dense" */
+ /* and have already been killed) */
+ DEBUG0 (("Newly null killed: %d\n", c)) ;
+ Col [c].shared2.order = --n_col2 ;
+ KILL_PRINCIPAL_COL (c) ;
+ }
+ else
+ {
+ /* set column length and set score */
+ assert (score >= 0) ;
+ assert (score <= n_col) ;
+ Col [c].length = col_length ;
+ Col [c].shared2.score = score ;
+ }
+ }
+ DEBUG0 (("Dense, null, and newly-null columns killed: %d\n",n_col-n_col2)) ;
+
+ /* At this point, all empty rows and columns are dead. All live columns */
+ /* are "clean" (containing no dead rows) and simplicial (no supercolumns */
+ /* yet). Rows may contain dead columns, but all live rows contain at */
+ /* least one live column. */
+
+#ifndef NDEBUG
+ debug_structures (n_row, n_col, Row, Col, A, n_col2) ;
+#endif
+
+ /* === Initialize degree lists ========================================== */
+
+#ifndef NDEBUG
+ debug_count = 0 ;
+#endif
+
+ /* clear the hash buckets */
+ for (c = 0 ; c <= n_col ; c++)
+ {
+ head [c] = EMPTY ;
+ }
+ min_score = n_col ;
+ /* place in reverse order, so low column indices are at the front */
+ /* of the lists. This is to encourage natural tie-breaking */
+ for (c = n_col-1 ; c >= 0 ; c--)
+ {
+ /* only add principal columns to degree lists */
+ if (COL_IS_ALIVE (c))
+ {
+ DEBUG4 (("place %d score %d minscore %d ncol %d\n",
+ c, Col [c].shared2.score, min_score, n_col)) ;
+
+ /* === Add columns score to DList =============================== */
+
+ score = Col [c].shared2.score ;
+
+ assert (min_score >= 0) ;
+ assert (min_score <= n_col) ;
+ assert (score >= 0) ;
+ assert (score <= n_col) ;
+ assert (head [score] >= EMPTY) ;
+
+ /* now add this column to dList at proper score location */
+ next_col = head [score] ;
+ Col [c].shared3.prev = EMPTY ;
+ Col [c].shared4.degree_next = next_col ;
+
+ /* if there already was a column with the same score, set its */
+ /* previous pointer to this new column */
+ if (next_col != EMPTY)
+ {
+ Col [next_col].shared3.prev = c ;
+ }
+ head [score] = c ;
+
+ /* see if this score is less than current min */
+ min_score = MIN (min_score, score) ;
+
+#ifndef NDEBUG
+ debug_count++ ;
+#endif
+ }
+ }
+
+#ifndef NDEBUG
+ DEBUG0 (("Live cols %d out of %d, non-princ: %d\n",
+ debug_count, n_col, n_col-debug_count)) ;
+ assert (debug_count == n_col2) ;
+ debug_deg_lists (n_row, n_col, Row, Col, head, min_score, n_col2, max_deg) ;
+#endif
+
+ /* === Return number of remaining columns, and max row degree =========== */
+
+ *p_n_col2 = n_col2 ;
+ *p_n_row2 = n_row2 ;
+ *p_max_deg = max_deg ;
+}
+
+
+/* ========================================================================== */
+/* === find_ordering ======================================================== */
+/* ========================================================================== */
+
+/*
+ Order the principal columns of the supercolumn form of the matrix
+ (no supercolumns on input). Uses a minimum approximate column minimum
+ degree ordering method. Not user-callable.
+*/
+
+PRIVATE int find_ordering /* return the number of garbage collections */
+(
+ /* === Parameters ======================================================= */
+
+ int n_row, /* number of rows of A */
+ int n_col, /* number of columns of A */
+ int Alen, /* size of A, 2*nnz + elbow_room or larger */
+ RowInfo Row [], /* of size n_row+1 */
+ ColInfo Col [], /* of size n_col+1 */
+ int A [], /* column form and row form of A */
+ int head [], /* of size n_col+1 */
+ int n_col2, /* Remaining columns to order */
+ int max_deg, /* Maximum row degree */
+ int pfree /* index of first free slot (2*nnz on entry) */
+)
+{
+ /* === Local variables ================================================== */
+
+ int k ; /* current pivot ordering step */
+ int pivot_col ; /* current pivot column */
+ int *cp ; /* a column pointer */
+ int *rp ; /* a row pointer */
+ int pivot_row ; /* current pivot row */
+ int *new_cp ; /* modified column pointer */
+ int *new_rp ; /* modified row pointer */
+ int pivot_row_start ; /* pointer to start of pivot row */
+ int pivot_row_degree ; /* # of columns in pivot row */
+ int pivot_row_length ; /* # of supercolumns in pivot row */
+ int pivot_col_score ; /* score of pivot column */
+ int needed_memory ; /* free space needed for pivot row */
+ int *cp_end ; /* pointer to the end of a column */
+ int *rp_end ; /* pointer to the end of a row */
+ int row ; /* a row index */
+ int col ; /* a column index */
+ int max_score ; /* maximum possible score */
+ int cur_score ; /* score of current column */
+ unsigned int hash ; /* hash value for supernode detection */
+ int head_column ; /* head of hash bucket */
+ int first_col ; /* first column in hash bucket */
+ int tag_mark ; /* marker value for mark array */
+ int row_mark ; /* Row [row].shared2.mark */
+ int set_difference ; /* set difference size of row with pivot row */
+ int min_score ; /* smallest column score */
+ int col_thickness ; /* "thickness" (# of columns in a supercol) */
+ int max_mark ; /* maximum value of tag_mark */
+ int pivot_col_thickness ; /* number of columns represented by pivot col */
+ int prev_col ; /* Used by Dlist operations. */
+ int next_col ; /* Used by Dlist operations. */
+ int ngarbage ; /* number of garbage collections performed */
+#ifndef NDEBUG
+ int debug_d ; /* debug loop counter */
+ int debug_step = 0 ; /* debug loop counter */
+#endif
+
+ /* === Initialization and clear mark ==================================== */
+
+ max_mark = INT_MAX - n_col ; /* INT_MAX defined in <limits.h> */
+ tag_mark = clear_mark (n_row, Row) ;
+ min_score = 0 ;
+ ngarbage = 0 ;
+ DEBUG0 (("Ordering.. n_col2=%d\n", n_col2)) ;
+
+ /* === Order the columns ================================================ */
+
+ for (k = 0 ; k < n_col2 ; /* 'k' is incremented below */)
+ {
+
+#ifndef NDEBUG
+ if (debug_step % 100 == 0)
+ {
+ DEBUG0 (("\n... Step k: %d out of n_col2: %d\n", k, n_col2)) ;
+ }
+ else
+ {
+ DEBUG1 (("\n----------Step k: %d out of n_col2: %d\n", k, n_col2)) ;
+ }
+ debug_step++ ;
+ debug_deg_lists (n_row, n_col, Row, Col, head,
+ min_score, n_col2-k, max_deg) ;
+ debug_matrix (n_row, n_col, Row, Col, A) ;
+#endif
+
+ /* === Select pivot column, and order it ============================ */
+
+ /* make sure degree list isn't empty */
+ assert (min_score >= 0) ;
+ assert (min_score <= n_col) ;
+ assert (head [min_score] >= EMPTY) ;
+
+#ifndef NDEBUG
+ for (debug_d = 0 ; debug_d < min_score ; debug_d++)
+ {
+ assert (head [debug_d] == EMPTY) ;
+ }
+#endif
+
+ /* get pivot column from head of minimum degree list */
+ while (head [min_score] == EMPTY && min_score < n_col)
+ {
+ min_score++ ;
+ }
+ pivot_col = head [min_score] ;
+ assert (pivot_col >= 0 && pivot_col <= n_col) ;
+ next_col = Col [pivot_col].shared4.degree_next ;
+ head [min_score] = next_col ;
+ if (next_col != EMPTY)
+ {
+ Col [next_col].shared3.prev = EMPTY ;
+ }
+
+ assert (COL_IS_ALIVE (pivot_col)) ;
+ DEBUG3 (("Pivot col: %d\n", pivot_col)) ;
+
+ /* remember score for defrag check */
+ pivot_col_score = Col [pivot_col].shared2.score ;
+
+ /* the pivot column is the kth column in the pivot order */
+ Col [pivot_col].shared2.order = k ;
+
+ /* increment order count by column thickness */
+ pivot_col_thickness = Col [pivot_col].shared1.thickness ;
+ k += pivot_col_thickness ;
+ assert (pivot_col_thickness > 0) ;
+
+ /* === Garbage_collection, if necessary ============================= */
+
+ needed_memory = MIN (pivot_col_score, n_col - k) ;
+ if (pfree + needed_memory >= Alen)
+ {
+ pfree = garbage_collection (n_row, n_col, Row, Col, A, &A [pfree]) ;
+ ngarbage++ ;
+ /* after garbage collection we will have enough */
+ assert (pfree + needed_memory < Alen) ;
+ /* garbage collection has wiped out the Row[].shared2.mark array */
+ tag_mark = clear_mark (n_row, Row) ;
+#ifndef NDEBUG
+ debug_matrix (n_row, n_col, Row, Col, A) ;
+#endif
+ }
+
+ /* === Compute pivot row pattern ==================================== */
+
+ /* get starting location for this new merged row */
+ pivot_row_start = pfree ;
+
+ /* initialize new row counts to zero */
+ pivot_row_degree = 0 ;
+
+ /* tag pivot column as having been visited so it isn't included */
+ /* in merged pivot row */
+ Col [pivot_col].shared1.thickness = -pivot_col_thickness ;
+
+ /* pivot row is the union of all rows in the pivot column pattern */
+ cp = &A [Col [pivot_col].start] ;
+ cp_end = cp + Col [pivot_col].length ;
+ while (cp < cp_end)
+ {
+ /* get a row */
+ row = *cp++ ;
+ DEBUG4 (("Pivot col pattern %d %d\n", ROW_IS_ALIVE (row), row)) ;
+ /* skip if row is dead */
+ if (ROW_IS_DEAD (row))
+ {
+ continue ;
+ }
+ rp = &A [Row [row].start] ;
+ rp_end = rp + Row [row].length ;
+ while (rp < rp_end)
+ {
+ /* get a column */
+ col = *rp++ ;
+ /* add the column, if alive and untagged */
+ col_thickness = Col [col].shared1.thickness ;
+ if (col_thickness > 0 && COL_IS_ALIVE (col))
+ {
+ /* tag column in pivot row */
+ Col [col].shared1.thickness = -col_thickness ;
+ assert (pfree < Alen) ;
+ /* place column in pivot row */
+ A [pfree++] = col ;
+ pivot_row_degree += col_thickness ;
+ }
+ }
+ }
+
+ /* clear tag on pivot column */
+ Col [pivot_col].shared1.thickness = pivot_col_thickness ;
+ max_deg = MAX (max_deg, pivot_row_degree) ;
+
+#ifndef NDEBUG
+ DEBUG3 (("check2\n")) ;
+ debug_mark (n_row, Row, tag_mark, max_mark) ;
+#endif
+
+ /* === Kill all rows used to construct pivot row ==================== */
+
+ /* also kill pivot row, temporarily */
+ cp = &A [Col [pivot_col].start] ;
+ cp_end = cp + Col [pivot_col].length ;
+ while (cp < cp_end)
+ {
+ /* may be killing an already dead row */
+ row = *cp++ ;
+ DEBUG2 (("Kill row in pivot col: %d\n", row)) ;
+ KILL_ROW (row) ;
+ }
+
+ /* === Select a row index to use as the new pivot row =============== */
+
+ pivot_row_length = pfree - pivot_row_start ;
+ if (pivot_row_length > 0)
+ {
+ /* pick the "pivot" row arbitrarily (first row in col) */
+ pivot_row = A [Col [pivot_col].start] ;
+ DEBUG2 (("Pivotal row is %d\n", pivot_row)) ;
+ }
+ else
+ {
+ /* there is no pivot row, since it is of zero length */
+ pivot_row = EMPTY ;
+ assert (pivot_row_length == 0) ;
+ }
+ assert (Col [pivot_col].length > 0 || pivot_row_length == 0) ;
+
+ /* === Approximate degree computation =============================== */
+
+ /* Here begins the computation of the approximate degree. The column */
+ /* score is the sum of the pivot row "length", plus the size of the */
+ /* set differences of each row in the column minus the pattern of the */
+ /* pivot row itself. The column ("thickness") itself is also */
+ /* excluded from the column score (we thus use an approximate */
+ /* external degree). */
+
+ /* The time taken by the following code (compute set differences, and */
+ /* add them up) is proportional to the size of the data structure */
+ /* being scanned - that is, the sum of the sizes of each column in */
+ /* the pivot row. Thus, the amortized time to compute a column score */
+ /* is proportional to the size of that column (where size, in this */
+ /* context, is the column "length", or the number of row indices */
+ /* in that column). The number of row indices in a column is */
+ /* monotonically non-decreasing, from the length of the original */
+ /* column on input to colamd. */
+
+ /* === Compute set differences ====================================== */
+
+ DEBUG1 (("** Computing set differences phase. **\n")) ;
+
+ /* pivot row is currently dead - it will be revived later. */
+
+ DEBUG2 (("Pivot row: ")) ;
+ /* for each column in pivot row */
+ rp = &A [pivot_row_start] ;
+ rp_end = rp + pivot_row_length ;
+ while (rp < rp_end)
+ {
+ col = *rp++ ;
+ assert (COL_IS_ALIVE (col) && col != pivot_col) ;
+ DEBUG2 (("Col: %d\n", col)) ;
+
+ /* clear tags used to construct pivot row pattern */
+ col_thickness = -Col [col].shared1.thickness ;
+ assert (col_thickness > 0) ;
+ Col [col].shared1.thickness = col_thickness ;
+
+ /* === Remove column from degree list =========================== */
+
+ cur_score = Col [col].shared2.score ;
+ prev_col = Col [col].shared3.prev ;
+ next_col = Col [col].shared4.degree_next ;
+ assert (cur_score >= 0) ;
+ assert (cur_score <= n_col) ;
+ assert (cur_score >= EMPTY) ;
+ if (prev_col == EMPTY)
+ {
+ head [cur_score] = next_col ;
+ }
+ else
+ {
+ Col [prev_col].shared4.degree_next = next_col ;
+ }
+ if (next_col != EMPTY)
+ {
+ Col [next_col].shared3.prev = prev_col ;
+ }
+
+ /* === Scan the column ========================================== */
+
+ cp = &A [Col [col].start] ;
+ cp_end = cp + Col [col].length ;
+ while (cp < cp_end)
+ {
+ /* get a row */
+ row = *cp++ ;
+ row_mark = Row [row].shared2.mark ;
+ /* skip if dead */
+ if (ROW_IS_MARKED_DEAD (row_mark))
+ {
+ continue ;
+ }
+ assert (row != pivot_row) ;
+ set_difference = row_mark - tag_mark ;
+ /* check if the row has been seen yet */
+ if (set_difference < 0)
+ {
+ assert (Row [row].shared1.degree <= max_deg) ;
+ set_difference = Row [row].shared1.degree ;
+ }
+ /* subtract column thickness from this row's set difference */
+ set_difference -= col_thickness ;
+ assert (set_difference >= 0) ;
+ /* absorb this row if the set difference becomes zero */
+ if (set_difference == 0)
+ {
+ DEBUG1 (("aggressive absorption. Row: %d\n", row)) ;
+ KILL_ROW (row) ;
+ }
+ else
+ {
+ /* save the new mark */
+ Row [row].shared2.mark = set_difference + tag_mark ;
+ }
+ }
+ }
+
+#ifndef NDEBUG
+ debug_deg_lists (n_row, n_col, Row, Col, head,
+ min_score, n_col2-k-pivot_row_degree, max_deg) ;
+#endif
+
+ /* === Add up set differences for each column ======================= */
+
+ DEBUG1 (("** Adding set differences phase. **\n")) ;
+
+ /* for each column in pivot row */
+ rp = &A [pivot_row_start] ;
+ rp_end = rp + pivot_row_length ;
+ while (rp < rp_end)
+ {
+ /* get a column */
+ col = *rp++ ;
+ assert (COL_IS_ALIVE (col) && col != pivot_col) ;
+ hash = 0 ;
+ cur_score = 0 ;
+ cp = &A [Col [col].start] ;
+ /* compact the column */
+ new_cp = cp ;
+ cp_end = cp + Col [col].length ;
+
+ DEBUG2 (("Adding set diffs for Col: %d.\n", col)) ;
+
+ while (cp < cp_end)
+ {
+ /* get a row */
+ row = *cp++ ;
+ assert(row >= 0 && row < n_row) ;
+ row_mark = Row [row].shared2.mark ;
+ /* skip if dead */
+ if (ROW_IS_MARKED_DEAD (row_mark))
+ {
+ continue ;
+ }
+ assert (row_mark > tag_mark) ;
+ /* compact the column */
+ *new_cp++ = row ;
+ /* compute hash function */
+ hash += row ;
+ /* add set difference */
+ cur_score += row_mark - tag_mark ;
+ /* integer overflow... */
+ cur_score = MIN (cur_score, n_col) ;
+ }
+
+ /* recompute the column's length */
+ Col [col].length = (int) (new_cp - &A [Col [col].start]) ;
+
+ /* === Further mass elimination ================================= */
+
+ if (Col [col].length == 0)
+ {
+ DEBUG1 (("further mass elimination. Col: %d\n", col)) ;
+ /* nothing left but the pivot row in this column */
+ KILL_PRINCIPAL_COL (col) ;
+ pivot_row_degree -= Col [col].shared1.thickness ;
+ assert (pivot_row_degree >= 0) ;
+ /* order it */
+ Col [col].shared2.order = k ;
+ /* increment order count by column thickness */
+ k += Col [col].shared1.thickness ;
+ }
+ else
+ {
+ /* === Prepare for supercolumn detection ==================== */
+
+ DEBUG2 (("Preparing supercol detection for Col: %d.\n", col)) ;
+
+ /* save score so far */
+ Col [col].shared2.score = cur_score ;
+
+ /* add column to hash table, for supercolumn detection */
+ hash %= n_col + 1 ;
+
+ DEBUG2 ((" Hash = %d, n_col = %d.\n", hash, n_col)) ;
+ assert (hash <= n_col) ;
+
+ head_column = head [hash] ;
+ if (head_column > EMPTY)
+ {
+ /* degree list "hash" is non-empty, use prev (shared3) of */
+ /* first column in degree list as head of hash bucket */
+ first_col = Col [head_column].shared3.headhash ;
+ Col [head_column].shared3.headhash = col ;
+ }
+ else
+ {
+ /* degree list "hash" is empty, use head as hash bucket */
+ first_col = - (head_column + 2) ;
+ head [hash] = - (col + 2) ;
+ }
+ Col [col].shared4.hash_next = first_col ;
+
+ /* save hash function in Col [col].shared3.hash */
+ Col [col].shared3.hash = (int) hash ;
+ assert (COL_IS_ALIVE (col)) ;
+ }
+ }
+
+ /* The approximate external column degree is now computed. */
+
+ /* === Supercolumn detection ======================================== */
+
+ DEBUG1 (("** Supercolumn detection phase. **\n")) ;
+
+ detect_super_cols (
+#ifndef NDEBUG
+ n_col, Row,
+#endif
+ Col, A, head, pivot_row_start, pivot_row_length) ;
+
+ /* === Kill the pivotal column ====================================== */
+
+ KILL_PRINCIPAL_COL (pivot_col) ;
+
+ /* === Clear mark =================================================== */
+
+ tag_mark += (max_deg + 1) ;
+ if (tag_mark >= max_mark)
+ {
+ DEBUG1 (("clearing tag_mark\n")) ;
+ tag_mark = clear_mark (n_row, Row) ;
+ }
+#ifndef NDEBUG
+ DEBUG3 (("check3\n")) ;
+ debug_mark (n_row, Row, tag_mark, max_mark) ;
+#endif
+
+ /* === Finalize the new pivot row, and column scores ================ */
+
+ DEBUG1 (("** Finalize scores phase. **\n")) ;
+
+ /* for each column in pivot row */
+ rp = &A [pivot_row_start] ;
+ /* compact the pivot row */
+ new_rp = rp ;
+ rp_end = rp + pivot_row_length ;
+ while (rp < rp_end)
+ {
+ col = *rp++ ;
+ /* skip dead columns */
+ if (COL_IS_DEAD (col))
+ {
+ continue ;
+ }
+ *new_rp++ = col ;
+ /* add new pivot row to column */
+ A [Col [col].start + (Col [col].length++)] = pivot_row ;
+
+ /* retrieve score so far and add on pivot row's degree. */
+ /* (we wait until here for this in case the pivot */
+ /* row's degree was reduced due to mass elimination). */
+ cur_score = Col [col].shared2.score + pivot_row_degree ;
+
+ /* calculate the max possible score as the number of */
+ /* external columns minus the 'k' value minus the */
+ /* columns thickness */
+ max_score = n_col - k - Col [col].shared1.thickness ;
+
+ /* make the score the external degree of the union-of-rows */
+ cur_score -= Col [col].shared1.thickness ;
+
+ /* make sure score is less or equal than the max score */
+ cur_score = MIN (cur_score, max_score) ;
+ assert (cur_score >= 0) ;
+
+ /* store updated score */
+ Col [col].shared2.score = cur_score ;
+
+ /* === Place column back in degree list ========================= */
+
+ assert (min_score >= 0) ;
+ assert (min_score <= n_col) ;
+ assert (cur_score >= 0) ;
+ assert (cur_score <= n_col) ;
+ assert (head [cur_score] >= EMPTY) ;
+ next_col = head [cur_score] ;
+ Col [col].shared4.degree_next = next_col ;
+ Col [col].shared3.prev = EMPTY ;
+ if (next_col != EMPTY)
+ {
+ Col [next_col].shared3.prev = col ;
+ }
+ head [cur_score] = col ;
+
+ /* see if this score is less than current min */
+ min_score = MIN (min_score, cur_score) ;
+
+ }
+
+#ifndef NDEBUG
+ debug_deg_lists (n_row, n_col, Row, Col, head,
+ min_score, n_col2-k, max_deg) ;
+#endif
+
+ /* === Resurrect the new pivot row ================================== */
+
+ if (pivot_row_degree > 0)
+ {
+ /* update pivot row length to reflect any cols that were killed */
+ /* during super-col detection and mass elimination */
+ Row [pivot_row].start = pivot_row_start ;
+ Row [pivot_row].length = (int) (new_rp - &A[pivot_row_start]) ;
+ Row [pivot_row].shared1.degree = pivot_row_degree ;
+ Row [pivot_row].shared2.mark = 0 ;
+ /* pivot row is no longer dead */
+ }
+ }
+
+ /* === All principal columns have now been ordered ====================== */
+
+ return (ngarbage) ;
+}
+
+
+/* ========================================================================== */
+/* === order_children ======================================================= */
+/* ========================================================================== */
+
+/*
+ The find_ordering routine has ordered all of the principal columns (the
+ representatives of the supercolumns). The non-principal columns have not
+ yet been ordered. This routine orders those columns by walking up the
+ parent tree (a column is a child of the column which absorbed it). The
+ final permutation vector is then placed in p [0 ... n_col-1], with p [0]
+ being the first column, and p [n_col-1] being the last. It doesn't look
+ like it at first glance, but be assured that this routine takes time linear
+ in the number of columns. Although not immediately obvious, the time
+ taken by this routine is O (n_col), that is, linear in the number of
+ columns. Not user-callable.
+*/
+
+PRIVATE void order_children
+(
+ /* === Parameters ======================================================= */
+
+ int n_col, /* number of columns of A */
+ ColInfo Col [], /* of size n_col+1 */
+ int p [] /* p [0 ... n_col-1] is the column permutation*/
+)
+{
+ /* === Local variables ================================================== */
+
+ int i ; /* loop counter for all columns */
+ int c ; /* column index */
+ int parent ; /* index of column's parent */
+ int order ; /* column's order */
+
+ /* === Order each non-principal column ================================== */
+
+ for (i = 0 ; i < n_col ; i++)
+ {
+ /* find an un-ordered non-principal column */
+ assert (COL_IS_DEAD (i)) ;
+ if (!COL_IS_DEAD_PRINCIPAL (i) && Col [i].shared2.order == EMPTY)
+ {
+ parent = i ;
+ /* once found, find its principal parent */
+ do
+ {
+ parent = Col [parent].shared1.parent ;
+ } while (!COL_IS_DEAD_PRINCIPAL (parent)) ;
+
+ /* now, order all un-ordered non-principal columns along path */
+ /* to this parent. collapse tree at the same time */
+ c = i ;
+ /* get order of parent */
+ order = Col [parent].shared2.order ;
+
+ do
+ {
+ assert (Col [c].shared2.order == EMPTY) ;
+
+ /* order this column */
+ Col [c].shared2.order = order++ ;
+ /* collaps tree */
+ Col [c].shared1.parent = parent ;
+
+ /* get immediate parent of this column */
+ c = Col [c].shared1.parent ;
+
+ /* continue until we hit an ordered column. There are */
+ /* guarranteed not to be anymore unordered columns */
+ /* above an ordered column */
+ } while (Col [c].shared2.order == EMPTY) ;
+
+ /* re-order the super_col parent to largest order for this group */
+ Col [parent].shared2.order = order ;
+ }
+ }
+
+ /* === Generate the permutation ========================================= */
+
+ for (c = 0 ; c < n_col ; c++)
+ {
+ p [Col [c].shared2.order] = c ;
+ }
+}
+
+
+/* ========================================================================== */
+/* === detect_super_cols ==================================================== */
+/* ========================================================================== */
+
+/*
+ Detects supercolumns by finding matches between columns in the hash buckets.
+ Check amongst columns in the set A [row_start ... row_start + row_length-1].
+ The columns under consideration are currently *not* in the degree lists,
+ and have already been placed in the hash buckets.
+
+ The hash bucket for columns whose hash function is equal to h is stored
+ as follows:
+
+ if head [h] is >= 0, then head [h] contains a degree list, so:
+
+ head [h] is the first column in degree bucket h.
+ Col [head [h]].headhash gives the first column in hash bucket h.
+
+ otherwise, the degree list is empty, and:
+
+ -(head [h] + 2) is the first column in hash bucket h.
+
+ For a column c in a hash bucket, Col [c].shared3.prev is NOT a "previous
+ column" pointer. Col [c].shared3.hash is used instead as the hash number
+ for that column. The value of Col [c].shared4.hash_next is the next column
+ in the same hash bucket.
+
+ Assuming no, or "few" hash collisions, the time taken by this routine is
+ linear in the sum of the sizes (lengths) of each column whose score has
+ just been computed in the approximate degree computation.
+ Not user-callable.
+*/
+
+PRIVATE void detect_super_cols
+(
+ /* === Parameters ======================================================= */
+
+#ifndef NDEBUG
+ /* these two parameters are only needed when debugging is enabled: */
+ int n_col, /* number of columns of A */
+ RowInfo Row [], /* of size n_row+1 */
+#endif
+ ColInfo Col [], /* of size n_col+1 */
+ int A [], /* row indices of A */
+ int head [], /* head of degree lists and hash buckets */
+ int row_start, /* pointer to set of columns to check */
+ int row_length /* number of columns to check */
+)
+{
+ /* === Local variables ================================================== */
+
+ int hash ; /* hash # for a column */
+ int *rp ; /* pointer to a row */
+ int c ; /* a column index */
+ int super_c ; /* column index of the column to absorb into */
+ int *cp1 ; /* column pointer for column super_c */
+ int *cp2 ; /* column pointer for column c */
+ int length ; /* length of column super_c */
+ int prev_c ; /* column preceding c in hash bucket */
+ int i ; /* loop counter */
+ int *rp_end ; /* pointer to the end of the row */
+ int col ; /* a column index in the row to check */
+ int head_column ; /* first column in hash bucket or degree list */
+ int first_col ; /* first column in hash bucket */
+
+ /* === Consider each column in the row ================================== */
+
+ rp = &A [row_start] ;
+ rp_end = rp + row_length ;
+ while (rp < rp_end)
+ {
+ col = *rp++ ;
+ if (COL_IS_DEAD (col))
+ {
+ continue ;
+ }
+
+ /* get hash number for this column */
+ hash = Col [col].shared3.hash ;
+ assert (hash <= n_col) ;
+
+ /* === Get the first column in this hash bucket ===================== */
+
+ head_column = head [hash] ;
+ if (head_column > EMPTY)
+ {
+ first_col = Col [head_column].shared3.headhash ;
+ }
+ else
+ {
+ first_col = - (head_column + 2) ;
+ }
+
+ /* === Consider each column in the hash bucket ====================== */
+
+ for (super_c = first_col ; super_c != EMPTY ;
+ super_c = Col [super_c].shared4.hash_next)
+ {
+ assert (COL_IS_ALIVE (super_c)) ;
+ assert (Col [super_c].shared3.hash == hash) ;
+ length = Col [super_c].length ;
+
+ /* prev_c is the column preceding column c in the hash bucket */
+ prev_c = super_c ;
+
+ /* === Compare super_c with all columns after it ================ */
+
+ for (c = Col [super_c].shared4.hash_next ;
+ c != EMPTY ; c = Col [c].shared4.hash_next)
+ {
+ assert (c != super_c) ;
+ assert (COL_IS_ALIVE (c)) ;
+ assert (Col [c].shared3.hash == hash) ;
+
+ /* not identical if lengths or scores are different */
+ if (Col [c].length != length ||
+ Col [c].shared2.score != Col [super_c].shared2.score)
+ {
+ prev_c = c ;
+ continue ;
+ }
+
+ /* compare the two columns */
+ cp1 = &A [Col [super_c].start] ;
+ cp2 = &A [Col [c].start] ;
+
+ for (i = 0 ; i < length ; i++)
+ {
+ /* the columns are "clean" (no dead rows) */
+ assert (ROW_IS_ALIVE (*cp1)) ;
+ assert (ROW_IS_ALIVE (*cp2)) ;
+ /* row indices will same order for both supercols, */
+ /* no gather scatter nessasary */
+ if (*cp1++ != *cp2++)
+ {
+ break ;
+ }
+ }
+
+ /* the two columns are different if the for-loop "broke" */
+ if (i != length)
+ {
+ prev_c = c ;
+ continue ;
+ }
+
+ /* === Got it! two columns are identical =================== */
+
+ assert (Col [c].shared2.score == Col [super_c].shared2.score) ;
+
+ Col [super_c].shared1.thickness += Col [c].shared1.thickness ;
+ Col [c].shared1.parent = super_c ;
+ KILL_NON_PRINCIPAL_COL (c) ;
+ /* order c later, in order_children() */
+ Col [c].shared2.order = EMPTY ;
+ /* remove c from hash bucket */
+ Col [prev_c].shared4.hash_next = Col [c].shared4.hash_next ;
+ }
+ }
+
+ /* === Empty this hash bucket ======================================= */
+
+ if (head_column > EMPTY)
+ {
+ /* corresponding degree list "hash" is not empty */
+ Col [head_column].shared3.headhash = EMPTY ;
+ }
+ else
+ {
+ /* corresponding degree list "hash" is empty */
+ head [hash] = EMPTY ;
+ }
+ }
+}
+
+
+/* ========================================================================== */
+/* === garbage_collection =================================================== */
+/* ========================================================================== */
+
+/*
+ Defragments and compacts columns and rows in the workspace A. Used when
+ all avaliable memory has been used while performing row merging. Returns
+ the index of the first free position in A, after garbage collection. The
+ time taken by this routine is linear is the size of the array A, which is
+ itself linear in the number of nonzeros in the input matrix.
+ Not user-callable.
+*/
+
+PRIVATE int garbage_collection /* returns the new value of pfree */
+(
+ /* === Parameters ======================================================= */
+
+ int n_row, /* number of rows */
+ int n_col, /* number of columns */
+ RowInfo Row [], /* row info */
+ ColInfo Col [], /* column info */
+ int A [], /* A [0 ... Alen-1] holds the matrix */
+ int *pfree /* &A [0] ... pfree is in use */
+)
+{
+ /* === Local variables ================================================== */
+
+ int *psrc ; /* source pointer */
+ int *pdest ; /* destination pointer */
+ int j ; /* counter */
+ int r ; /* a row index */
+ int c ; /* a column index */
+ int length ; /* length of a row or column */
+
+#ifndef NDEBUG
+ int debug_rows ;
+ DEBUG0 (("Defrag..\n")) ;
+ for (psrc = &A[0] ; psrc < pfree ; psrc++) assert (*psrc >= 0) ;
+ debug_rows = 0 ;
+#endif
+
+ /* === Defragment the columns =========================================== */
+
+ pdest = &A[0] ;
+ for (c = 0 ; c < n_col ; c++)
+ {
+ if (COL_IS_ALIVE (c))
+ {
+ psrc = &A [Col [c].start] ;
+
+ /* move and compact the column */
+ assert (pdest <= psrc) ;
+ Col [c].start = (int) (pdest - &A [0]) ;
+ length = Col [c].length ;
+ for (j = 0 ; j < length ; j++)
+ {
+ r = *psrc++ ;
+ if (ROW_IS_ALIVE (r))
+ {
+ *pdest++ = r ;
+ }
+ }
+ Col [c].length = (int) (pdest - &A [Col [c].start]) ;
+ }
+ }
+
+ /* === Prepare to defragment the rows =================================== */
+
+ for (r = 0 ; r < n_row ; r++)
+ {
+ if (ROW_IS_ALIVE (r))
+ {
+ if (Row [r].length == 0)
+ {
+ /* this row is of zero length. cannot compact it, so kill it */
+ DEBUG0 (("Defrag row kill\n")) ;
+ KILL_ROW (r) ;
+ }
+ else
+ {
+ /* save first column index in Row [r].shared2.first_column */
+ psrc = &A [Row [r].start] ;
+ Row [r].shared2.first_column = *psrc ;
+ assert (ROW_IS_ALIVE (r)) ;
+ /* flag the start of the row with the one's complement of row */
+ *psrc = ONES_COMPLEMENT (r) ;
+#ifndef NDEBUG
+ debug_rows++ ;
+#endif
+ }
+ }
+ }
+
+ /* === Defragment the rows ============================================== */
+
+ psrc = pdest ;
+ while (psrc < pfree)
+ {
+ /* find a negative number ... the start of a row */
+ if (*psrc++ < 0)
+ {
+ psrc-- ;
+ /* get the row index */
+ r = ONES_COMPLEMENT (*psrc) ;
+ assert (r >= 0 && r < n_row) ;
+ /* restore first column index */
+ *psrc = Row [r].shared2.first_column ;
+ assert (ROW_IS_ALIVE (r)) ;
+
+ /* move and compact the row */
+ assert (pdest <= psrc) ;
+ Row [r].start = (int) (pdest - &A [0]) ;
+ length = Row [r].length ;
+ for (j = 0 ; j < length ; j++)
+ {
+ c = *psrc++ ;
+ if (COL_IS_ALIVE (c))
+ {
+ *pdest++ = c ;
+ }
+ }
+ Row [r].length = (int) (pdest - &A [Row [r].start]) ;
+#ifndef NDEBUG
+ debug_rows-- ;
+#endif
+ }
+ }
+ /* ensure we found all the rows */
+ assert (debug_rows == 0) ;
+
+ /* === Return the new value of pfree ==================================== */
+
+ return ((int) (pdest - &A [0])) ;
+}
+
+
+/* ========================================================================== */
+/* === clear_mark =========================================================== */
+/* ========================================================================== */
+
+/*
+ Clears the Row [].shared2.mark array, and returns the new tag_mark.
+ Return value is the new tag_mark. Not user-callable.
+*/
+
+PRIVATE int clear_mark /* return the new value for tag_mark */
+(
+ /* === Parameters ======================================================= */
+
+ int n_row, /* number of rows in A */
+ RowInfo Row [] /* Row [0 ... n_row-1].shared2.mark is set to zero */
+)
+{
+ /* === Local variables ================================================== */
+
+ int r ;
+
+ DEBUG0 (("Clear mark\n")) ;
+ for (r = 0 ; r < n_row ; r++)
+ {
+ if (ROW_IS_ALIVE (r))
+ {
+ Row [r].shared2.mark = 0 ;
+ }
+ }
+ return (1) ;
+}
+
+
+/* ========================================================================== */
+/* === debugging routines =================================================== */
+/* ========================================================================== */
+
+/* When debugging is disabled, the remainder of this file is ignored. */
+
+#ifndef NDEBUG
+
+
+/* ========================================================================== */
+/* === debug_structures ===================================================== */
+/* ========================================================================== */
+
+/*
+ At this point, all empty rows and columns are dead. All live columns
+ are "clean" (containing no dead rows) and simplicial (no supercolumns
+ yet). Rows may contain dead columns, but all live rows contain at
+ least one live column.
+*/
+
+PRIVATE void debug_structures
+(
+ /* === Parameters ======================================================= */
+
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int A [],
+ int n_col2
+)
+{
+ /* === Local variables ================================================== */
+
+ int i ;
+ int c ;
+ int *cp ;
+ int *cp_end ;
+ int len ;
+ int score ;
+ int r ;
+ int *rp ;
+ int *rp_end ;
+ int deg ;
+
+ /* === Check A, Row, and Col ============================================ */
+
+ for (c = 0 ; c < n_col ; c++)
+ {
+ if (COL_IS_ALIVE (c))
+ {
+ len = Col [c].length ;
+ score = Col [c].shared2.score ;
+ DEBUG4 (("initial live col %5d %5d %5d\n", c, len, score)) ;
+ assert (len > 0) ;
+ assert (score >= 0) ;
+ assert (Col [c].shared1.thickness == 1) ;
+ cp = &A [Col [c].start] ;
+ cp_end = cp + len ;
+ while (cp < cp_end)
+ {
+ r = *cp++ ;
+ assert (ROW_IS_ALIVE (r)) ;
+ }
+ }
+ else
+ {
+ i = Col [c].shared2.order ;
+ assert (i >= n_col2 && i < n_col) ;
+ }
+ }
+
+ for (r = 0 ; r < n_row ; r++)
+ {
+ if (ROW_IS_ALIVE (r))
+ {
+ i = 0 ;
+ len = Row [r].length ;
+ deg = Row [r].shared1.degree ;
+ assert (len > 0) ;
+ assert (deg > 0) ;
+ rp = &A [Row [r].start] ;
+ rp_end = rp + len ;
+ while (rp < rp_end)
+ {
+ c = *rp++ ;
+ if (COL_IS_ALIVE (c))
+ {
+ i++ ;
+ }
+ }
+ assert (i > 0) ;
+ }
+ }
+}
+
+
+/* ========================================================================== */
+/* === debug_deg_lists ====================================================== */
+/* ========================================================================== */
+
+/*
+ Prints the contents of the degree lists. Counts the number of columns
+ in the degree list and compares it to the total it should have. Also
+ checks the row degrees.
+*/
+
+PRIVATE void debug_deg_lists
+(
+ /* === Parameters ======================================================= */
+
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int head [],
+ int min_score,
+ int should,
+ int max_deg
+)
+{
+ /* === Local variables ================================================== */
+
+ int deg ;
+ int col ;
+ int have ;
+ int row ;
+
+ /* === Check the degree lists =========================================== */
+
+ if (n_col > 10000 && debug_colamd <= 0)
+ {
+ return ;
+ }
+ have = 0 ;
+ DEBUG4 (("Degree lists: %d\n", min_score)) ;
+ for (deg = 0 ; deg <= n_col ; deg++)
+ {
+ col = head [deg] ;
+ if (col == EMPTY)
+ {
+ continue ;
+ }
+ DEBUG4 (("%d:", deg)) ;
+ while (col != EMPTY)
+ {
+ DEBUG4 ((" %d", col)) ;
+ have += Col [col].shared1.thickness ;
+ assert (COL_IS_ALIVE (col)) ;
+ col = Col [col].shared4.degree_next ;
+ }
+ DEBUG4 (("\n")) ;
+ }
+ DEBUG4 (("should %d have %d\n", should, have)) ;
+ assert (should == have) ;
+
+ /* === Check the row degrees ============================================ */
+
+ if (n_row > 10000 && debug_colamd <= 0)
+ {
+ return ;
+ }
+ for (row = 0 ; row < n_row ; row++)
+ {
+ if (ROW_IS_ALIVE (row))
+ {
+ assert (Row [row].shared1.degree <= max_deg) ;
+ }
+ }
+}
+
+
+/* ========================================================================== */
+/* === debug_mark =========================================================== */
+/* ========================================================================== */
+
+/*
+ Ensures that the tag_mark is less that the maximum and also ensures that
+ each entry in the mark array is less than the tag mark.
+*/
+
+PRIVATE void debug_mark
+(
+ /* === Parameters ======================================================= */
+
+ int n_row,
+ RowInfo Row [],
+ int tag_mark,
+ int max_mark
+)
+{
+ /* === Local variables ================================================== */
+
+ int r ;
+
+ /* === Check the Row marks ============================================== */
+
+ assert (tag_mark > 0 && tag_mark <= max_mark) ;
+ if (n_row > 10000 && debug_colamd <= 0)
+ {
+ return ;
+ }
+ for (r = 0 ; r < n_row ; r++)
+ {
+ assert (Row [r].shared2.mark < tag_mark) ;
+ }
+}
+
+
+/* ========================================================================== */
+/* === debug_matrix ========================================================= */
+/* ========================================================================== */
+
+/*
+ Prints out the contents of the columns and the rows.
+*/
+
+PRIVATE void debug_matrix
+(
+ /* === Parameters ======================================================= */
+
+ int n_row,
+ int n_col,
+ RowInfo Row [],
+ ColInfo Col [],
+ int A []
+)
+{
+ /* === Local variables ================================================== */
+
+ int r ;
+ int c ;
+ int *rp ;
+ int *rp_end ;
+ int *cp ;
+ int *cp_end ;
+
+ /* === Dump the rows and columns of the matrix ========================== */
+
+ if (debug_colamd < 3)
+ {
+ return ;
+ }
+ DEBUG3 (("DUMP MATRIX:\n")) ;
+ for (r = 0 ; r < n_row ; r++)
+ {
+ DEBUG3 (("Row %d alive? %d\n", r, ROW_IS_ALIVE (r))) ;
+ if (ROW_IS_DEAD (r))
+ {
+ continue ;
+ }
+ DEBUG3 (("start %d length %d degree %d\n",
+ Row [r].start, Row [r].length, Row [r].shared1.degree)) ;
+ rp = &A [Row [r].start] ;
+ rp_end = rp + Row [r].length ;
+ while (rp < rp_end)
+ {
+ c = *rp++ ;
+ DEBUG3 ((" %d col %d\n", COL_IS_ALIVE (c), c)) ;
+ }
+ }
+
+ for (c = 0 ; c < n_col ; c++)
+ {
+ DEBUG3 (("Col %d alive? %d\n", c, COL_IS_ALIVE (c))) ;
+ if (COL_IS_DEAD (c))
+ {
+ continue ;
+ }
+ DEBUG3 (("start %d length %d shared1 %d shared2 %d\n",
+ Col [c].start, Col [c].length,
+ Col [c].shared1.thickness, Col [c].shared2.score)) ;
+ cp = &A [Col [c].start] ;
+ cp_end = cp + Col [c].length ;
+ while (cp < cp_end)
+ {
+ r = *cp++ ;
+ DEBUG3 ((" %d row %d\n", ROW_IS_ALIVE (r), r)) ;
+ }
+ }
+}
+
+#endif
+