1 files changed, 30 insertions, 9 deletions

diff --git a/extern/ceres/internal/ceres/cgnr_solver.cc b/extern/ceres/internal/ceres/cgnr_solver.cc
index 61fae758d5b..9dba1cfb4a8 100644
--- a/extern/ceres/internal/ceres/cgnr_solver.cc
+++ b/extern/ceres/internal/ceres/cgnr_solver.cc
@@ -35,6 +35,7 @@
 #include "ceres/conjugate_gradients_solver.h"
 #include "ceres/internal/eigen.h"
 #include "ceres/linear_solver.h"
+#include "ceres/subset_preconditioner.h"
 #include "ceres/wall_time.h"
 #include "glog/logging.h"
 
@@ -42,14 +43,19 @@ namespace ceres {
 namespace internal {
 
 CgnrSolver::CgnrSolver(const LinearSolver::Options& options)
-  : options_(options),
-    preconditioner_(NULL) {
+    : options_(options) {
   if (options_.preconditioner_type != JACOBI &&
-      options_.preconditioner_type != IDENTITY) {
-    LOG(FATAL) << "CGNR only supports IDENTITY and JACOBI preconditioners.";
+      options_.preconditioner_type != IDENTITY &&
+      options_.preconditioner_type != SUBSET) {
+    LOG(FATAL)
+        << "Preconditioner = "
+        << PreconditionerTypeToString(options_.preconditioner_type) << ". "
+        << "Congratulations, you found a bug in Ceres. Please report it.";
   }
 }
 
+CgnrSolver::~CgnrSolver() {}
+
 LinearSolver::Summary CgnrSolver::SolveImpl(
     BlockSparseMatrix* A,
     const double* b,
@@ -62,16 +68,31 @@ LinearSolver::Summary CgnrSolver::SolveImpl(
   z.setZero();
   A->LeftMultiply(b, z.data());
 
-  // Precondition if necessary.
-  LinearSolver::PerSolveOptions cg_per_solve_options = per_solve_options;
-  if (options_.preconditioner_type == JACOBI) {
-    if (preconditioner_.get() == NULL) {
+  if (!preconditioner_) {
+    if (options_.preconditioner_type == JACOBI) {
       preconditioner_.reset(new BlockJacobiPreconditioner(*A));
+    } else if (options_.preconditioner_type == SUBSET) {
+      Preconditioner::Options preconditioner_options;
+      preconditioner_options.type = SUBSET;
+      preconditioner_options.subset_preconditioner_start_row_block =
+          options_.subset_preconditioner_start_row_block;
+      preconditioner_options.sparse_linear_algebra_library_type =
+          options_.sparse_linear_algebra_library_type;
+      preconditioner_options.use_postordering = options_.use_postordering;
+      preconditioner_options.num_threads = options_.num_threads;
+      preconditioner_options.context = options_.context;
+      preconditioner_.reset(
+          new SubsetPreconditioner(preconditioner_options, *A));
     }
+  }
+
+  if (preconditioner_) {
     preconditioner_->Update(*A, per_solve_options.D);
-    cg_per_solve_options.preconditioner = preconditioner_.get();
   }
 
+  LinearSolver::PerSolveOptions cg_per_solve_options = per_solve_options;
+  cg_per_solve_options.preconditioner = preconditioner_.get();
+
   // Solve (AtA + DtD)x = z (= Atb).
   VectorRef(x, A->num_cols()).setZero();
   CgnrLinearOperator lhs(*A, per_solve_options.D);