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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
* The Original Code is Copyright (C) 2015 Blender Foundation.
* All rights reserved.
*/
/** \file blender/depsgraph/intern/builder/deg_builder_cycle.cc
* \ingroup depsgraph
*/
#include "intern/builder/deg_builder_cycle.h"
// TOO(sergey): Use some wrappers over those?
#include <cstdio>
#include <cstdlib>
#include "BLI_utildefines.h"
#include "BLI_stack.h"
#include "util/deg_util_foreach.h"
#include "intern/nodes/deg_node.h"
#include "intern/nodes/deg_node_component.h"
#include "intern/nodes/deg_node_operation.h"
#include "intern/depsgraph.h"
namespace DEG {
namespace {
typedef enum eCyclicCheckVisitedState {
/* Not is not visited at all during traversal. */
NODE_NOT_VISITED = 0,
/* Node has been visited during traversal and not in current stack. */
NODE_VISITED = 1,
/* Node has been visited during traversal and is in current stack. */
NODE_IN_STACK = 2,
} eCyclicCheckVisitedState;
struct StackEntry {
OperationDepsNode *node;
StackEntry *from;
DepsRelation *via_relation;
};
struct CyclesSolverState {
CyclesSolverState(Depsgraph *graph)
: graph(graph),
traversal_stack(BLI_stack_new(sizeof(StackEntry),
"DEG detect cycles stack")),
num_cycles(0)
{
/* pass */
}
~CyclesSolverState() {
BLI_stack_free(traversal_stack);
if (num_cycles != 0) {
printf("Detected %d dependency cycles\n", num_cycles);
}
}
Depsgraph *graph;
BLI_Stack *traversal_stack;
int num_cycles;
};
BLI_INLINE void set_node_visited_state(DepsNode *node,
eCyclicCheckVisitedState state)
{
node->done = (node->done & ~0x3) | (int)state;
}
BLI_INLINE eCyclicCheckVisitedState get_node_visited_state(DepsNode *node)
{
return (eCyclicCheckVisitedState)(node->done & 0x3);
}
BLI_INLINE void set_node_num_visited_children(DepsNode *node, int num_children)
{
node->done = (node->done & 0x3) | (num_children << 2);
}
BLI_INLINE int get_node_num_visited_children(DepsNode *node)
{
return node->done >> 2;
}
void schedule_node_to_stack(CyclesSolverState *state, OperationDepsNode *node)
{
StackEntry entry;
entry.node = node;
entry.from = NULL;
entry.via_relation = NULL;
BLI_stack_push(state->traversal_stack, &entry);
set_node_visited_state(node, NODE_IN_STACK);
}
/* Schedule leaf nodes (node without input links) for traversal. */
void schedule_leaf_nodes(CyclesSolverState *state)
{
foreach (OperationDepsNode *node, state->graph->operations) {
bool has_inlinks = false;
foreach (DepsRelation *rel, node->inlinks) {
if (rel->from->type == DEG_NODE_TYPE_OPERATION) {
has_inlinks = true;
}
}
node->done = 0;
if (has_inlinks == false) {
schedule_node_to_stack(state, node);
}
else {
set_node_visited_state(node, NODE_NOT_VISITED);
}
}
}
/* Schedule node which was not checked yet for being belong to
* any of dependency cycle.
*/
bool schedule_non_checked_node(CyclesSolverState *state)
{
foreach (OperationDepsNode *node, state->graph->operations) {
if (get_node_visited_state(node) == NODE_NOT_VISITED) {
schedule_node_to_stack(state, node);
return true;
}
}
return false;
}
/* Solve cycles with all nodes which are scheduled for traversal. */
void solve_cycles(CyclesSolverState *state)
{
BLI_Stack *traversal_stack = state->traversal_stack;
while (!BLI_stack_is_empty(traversal_stack)) {
StackEntry *entry = (StackEntry *)BLI_stack_peek(traversal_stack);
OperationDepsNode *node = entry->node;
bool all_child_traversed = true;
const int num_visited = get_node_num_visited_children(node);
for (int i = num_visited; i < node->outlinks.size(); ++i) {
DepsRelation *rel = node->outlinks[i];
if (rel->to->type == DEG_NODE_TYPE_OPERATION) {
OperationDepsNode *to = (OperationDepsNode *)rel->to;
eCyclicCheckVisitedState to_state = get_node_visited_state(to);
if (to_state == NODE_IN_STACK) {
printf("Dependency cycle detected:\n");
printf(" '%s' depends on '%s' through '%s'\n",
to->full_identifier().c_str(),
node->full_identifier().c_str(),
rel->name);
StackEntry *current = entry;
while (current->node != to) {
BLI_assert(current != NULL);
printf(" '%s' depends on '%s' through '%s'\n",
current->node->full_identifier().c_str(),
current->from->node->full_identifier().c_str(),
current->via_relation->name);
current = current->from;
}
/* TODO(sergey): So called russian roulette cycle solver. */
rel->flag |= DEPSREL_FLAG_CYCLIC;
++state->num_cycles;
}
else if (to_state == NODE_NOT_VISITED) {
StackEntry new_entry;
new_entry.node = to;
new_entry.from = entry;
new_entry.via_relation = rel;
BLI_stack_push(traversal_stack, &new_entry);
set_node_visited_state(node, NODE_IN_STACK);
all_child_traversed = false;
set_node_num_visited_children(node, i);
break;
}
}
}
if (all_child_traversed) {
set_node_visited_state(node, NODE_VISITED);
BLI_stack_discard(traversal_stack);
}
}
}
} // namespace
void deg_graph_detect_cycles(Depsgraph *graph)
{
CyclesSolverState state(graph);
/* First we solve cycles which are reachable from leaf nodes. */
schedule_leaf_nodes(&state);
solve_cycles(&state);
/* We are not done yet. It is possible to have closed loop cycle,
* for example A -> B -> C -> A. These nodes were not scheduled
* yet (since they all have inlinks), and were not traversed since
* nobody else points to them.
*/
while (schedule_non_checked_node(&state)) {
solve_cycles(&state);
}
}
} // namespace DEG
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