Add logging for sparse Cholesky factorization using Eigen

Print information about the fill-in when using Eigen to perform
Simplicial sparse Cholesky factorization.

Change-Id: I09013b7f4ed2f6c55ae8ce8922447e23d63580a8

internal/ceres/schur_complement_solver.cc

diff --git a/internal/ceres/schur_complement_solver.cc b/internal/ceres/schur_complement_solver.cc
index 2491060..6544983 100644
--- a/internal/ceres/schur_complement_solver.cc
+++ b/internal/ceres/schur_complement_solver.cc
@@ -33,6 +33,7 @@
 #include <algorithm>
 #include <ctime>
 #include <set>
+#include <sstream>
 #include <vector>
 
 #include "ceres/block_random_access_dense_matrix.h"
@@ -563,6 +564,12 @@
     // worse than the one computed using the block version of the
     // algorithm.
     simplicial_ldlt_->analyzePattern(eigen_lhs);
+    if (VLOG_IS_ON(2)) {
+      std::stringstream ss;
+      simplicial_ldlt_->dumpMemory(ss);
+      VLOG(2) << "Symbolic Analysis\n"
+              << ss.str();
+    }
     event_logger.AddEvent("Analysis");
     if (simplicial_ldlt_->info() != Eigen::Success) {
       summary.termination_type = LINEAR_SOLVER_FATAL_ERROR;

internal/ceres/sparse_normal_cholesky_solver.cc

diff --git a/internal/ceres/sparse_normal_cholesky_solver.cc b/internal/ceres/sparse_normal_cholesky_solver.cc
index ed00879..a4c2c76 100644
--- a/internal/ceres/sparse_normal_cholesky_solver.cc
+++ b/internal/ceres/sparse_normal_cholesky_solver.cc
@@ -33,6 +33,7 @@
 #include <algorithm>
 #include <cstring>
 #include <ctime>
+#include <sstream>
 
 #include "ceres/compressed_row_sparse_matrix.h"
 #include "ceres/cxsparse.h"
@@ -71,6 +72,12 @@
 
   if (do_symbolic_analysis) {
     solver->analyzePattern(lhs);
+    if (VLOG_IS_ON(2)) {
+      std::stringstream ss;
+      solver->dumpMemory(ss);
+      VLOG(2) << "Symbolic Analysis\n"
+              << ss.str();
+    }
     event_logger->AddEvent("Analyze");
     if (solver->info() != Eigen::Success) {
       summary.termination_type = LINEAR_SOLVER_FATAL_ERROR;