ITERATIVE_SCHUR works with no f-blocks.
When the Schur complement is of size zero,
i.e. none of the parameter blocks interact
with each other, the ITERATIVE_SCHUR linear
solver crashes due to some checks that are
triggered in the SCHUR_JACOBI preconditioner.
This patch adds logic to detect this condition
and to deal with it and adds tests that verify
the fix.
Thanks to Soohyun Bae for reporting this bug.
Change-Id: If29ddf32463cbb1960414fff0e29bbf0d2ee7989
diff --git a/internal/ceres/iterative_schur_complement_solver.cc b/internal/ceres/iterative_schur_complement_solver.cc
index 0b1cb89..1aac565 100644
--- a/internal/ceres/iterative_schur_complement_solver.cc
+++ b/internal/ceres/iterative_schur_complement_solver.cc
@@ -78,6 +78,17 @@
}
schur_complement_->Init(*A, per_solve_options.D, b);
+ const int num_schur_complement_blocks =
+ A->block_structure()->cols.size() - options_.elimination_groups[0];
+ if (num_schur_complement_blocks == 0) {
+ VLOG(2) << "No parameter blocks left in the schur complement.";
+ LinearSolver::Summary cg_summary;
+ cg_summary.num_iterations = 0;
+ cg_summary.termination_type = TOLERANCE;
+ schur_complement_->BackSubstitute(NULL, x);
+ return cg_summary;
+ }
+
// Initialize the solution to the Schur complement system to zero.
//
// TODO(sameeragarwal): There maybe a better initialization than an
@@ -116,16 +127,16 @@
case SCHUR_JACOBI:
if (preconditioner_.get() == NULL) {
preconditioner_.reset(
- new SchurJacobiPreconditioner(
- *A->block_structure(), preconditioner_options));
+ new SchurJacobiPreconditioner(*A->block_structure(),
+ preconditioner_options));
}
break;
case CLUSTER_JACOBI:
case CLUSTER_TRIDIAGONAL:
if (preconditioner_.get() == NULL) {
preconditioner_.reset(
- new VisibilityBasedPreconditioner(
- *A->block_structure(), preconditioner_options));
+ new VisibilityBasedPreconditioner(*A->block_structure(),
+ preconditioner_options));
}
break;
default:
