Expand reporting of timing information.

1. Add an ExecutionSummary object to record execution
   information about Ceres objects.
2. Add an EventLogger object to log events in a function call.
3. Add a ScopedExecutionTimer object to log times in ExecutionSummary.
4. Instrument ProgramEvaluator and all the linear solvers
   to report their timing statistics.
5. Connect the timing statistics to Summary::FullReport.
6. Add high precision timer on unix systems using
   gettimeofday() call.
7. Various minor clean ups all around.

Change-Id: I5e09804b730b09535484124be7dbc1c58eccd1d4

internal/ceres/dense_qr_solver.cc

diff --git a/internal/ceres/dense_qr_solver.cc b/internal/ceres/dense_qr_solver.cc
index 7aec450..21b6b15 100644
--- a/internal/ceres/dense_qr_solver.cc
+++ b/internal/ceres/dense_qr_solver.cc
@@ -34,10 +34,11 @@
 
 #include "Eigen/Dense"
 #include "ceres/dense_sparse_matrix.h"
-#include "ceres/linear_solver.h"
 #include "ceres/internal/eigen.h"
 #include "ceres/internal/scoped_ptr.h"
+#include "ceres/linear_solver.h"
 #include "ceres/types.h"
+#include "ceres/wall_time.h"
 
 namespace ceres {
 namespace internal {
@@ -50,10 +51,10 @@
     const double* b,
     const LinearSolver::PerSolveOptions& per_solve_options,
     double* x) {
+  EventLogger event_logger("DenseQRSolver::Solve");
+
   const int num_rows = A->num_rows();
   const int num_cols = A->num_cols();
-  VLOG(2) << "DenseQRSolver: "
-          << num_rows << " x " << num_cols << " system.";
 
   if (per_solve_options.D != NULL) {
     // Temporarily append a diagonal block to the A matrix, but undo
@@ -68,9 +69,11 @@
     rhs_.setZero();
   }
   rhs_.head(num_rows) = ConstVectorRef(b, num_rows);
+  event_logger.AddEvent("Setup");
 
   // Solve the system.
   VectorRef(x, num_cols) = A->matrix().colPivHouseholderQr().solve(rhs_);
+  event_logger.AddEvent("Solve");
 
   if (per_solve_options.D != NULL) {
     // Undo the modifications to the matrix A.
@@ -83,6 +86,8 @@
   LinearSolver::Summary summary;
   summary.num_iterations = 1;
   summary.termination_type = TOLERANCE;
+
+  event_logger.AddEvent("TearDown");
   return summary;
 }