Add some time logging to bundle_adjuster.cc

Change-Id: I0deec65ec8d612a133748a242fe50d8e154f2704

examples/CMakeLists.txt

diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index 27a903c..e3ba5c4 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -67,7 +67,7 @@
 target_link_libraries(robust_curve_fitting PRIVATE absl::log_initialize Ceres::ceres)
 
 add_executable(simple_bundle_adjuster simple_bundle_adjuster.cc)
-target_link_libraries(simple_bundle_adjuster PRIVATE absl::log_initialize Ceres::ceres )
+target_link_libraries(simple_bundle_adjuster PRIVATE absl::log_initialize absl::time Ceres::ceres)
 
 add_executable(bicubic_interpolation bicubic_interpolation.cc)
 target_link_libraries(bicubic_interpolation PRIVATE absl::log_initialize Ceres::ceres)

examples/bundle_adjuster.cc

diff --git a/examples/bundle_adjuster.cc b/examples/bundle_adjuster.cc
index ecec6bf..5b25d6f 100644
--- a/examples/bundle_adjuster.cc
+++ b/examples/bundle_adjuster.cc
@@ -65,6 +65,7 @@
 #include "absl/log/check.h"
 #include "absl/log/initialize.h"
 #include "absl/log/log.h"
+#include "absl/time/time.h"
 #include "bal_problem.h"
 #include "ceres/ceres.h"
 #include "snavely_reprojection_error.h"
@@ -304,6 +305,7 @@
 }
 
 void BuildProblem(BALProblem* bal_problem, Problem* problem) {
+  const absl::Time start_time = absl::Now();
   const int point_block_size = bal_problem->point_block_size();
   const int camera_block_size = bal_problem->camera_block_size();
   double* points = bal_problem->mutable_points();
@@ -344,11 +346,11 @@
       problem->SetManifold(cameras + camera_block_size * i, camera_manifold);
     }
   }
+  LOG(INFO) << "Time to build problem: " << absl::Now() - start_time;
 }
 
 void SolveProblem(const char* filename) {
   BALProblem bal_problem(filename, absl::GetFlag(FLAGS_use_quaternions));
-
   if (!absl::GetFlag(FLAGS_initial_ply).empty()) {
     bal_problem.WriteToPLYFile(absl::GetFlag(FLAGS_initial_ply));
   }