diff --git a/include/ceres/iteration_callback.h b/include/ceres/iteration_callback.h
index 6d7720c..29157d3 100644
--- a/include/ceres/iteration_callback.h
+++ b/include/ceres/iteration_callback.h
@@ -91,15 +91,15 @@
   // Newton step.
   int linear_solver_iterations;
 
-  // TODO(sameeragarwal): Change the following two to use a higher
-  // precision timer using clock_gettime.
-  //
   // Time (in seconds) spent inside the minimizer loop in the current
   // iteration.
-  int iteration_time_sec;
+  double iteration_time_in_seconds;
 
   // Time (in seconds) spent inside the trust region step solver.
-  int step_solver_time_sec;
+  double step_solver_time_in_seconds;
+
+  // Time (in seconds) since the user called Solve().
+  double cumulative_time_in_seconds;
 };
 
 // Interface for specifying callbacks that are executed at the end of
diff --git a/include/ceres/solver.h b/include/ceres/solver.h
index 12351ab..5ca15e9 100644
--- a/include/ceres/solver.h
+++ b/include/ceres/solver.h
@@ -59,7 +59,7 @@
     Options() {
       trust_region_strategy_type = LEVENBERG_MARQUARDT;
       max_num_iterations = 50;
-      max_solver_time_sec = 1e9;
+      max_solver_time_in_seconds = 1e9;
       num_threads = 1;
       initial_trust_region_radius = 1e4;
       max_trust_region_radius = 1e16;
@@ -117,7 +117,7 @@
     int max_num_iterations;
 
     // Maximum time for which the minimizer should run for.
-    double max_solver_time_sec;
+    double max_solver_time_in_seconds;
 
     // Number of threads used by Ceres for evaluating the cost and
     // jacobians.
@@ -377,8 +377,21 @@
     int num_successful_steps;
     int num_unsuccessful_steps;
 
+    // When the user calls Solve, before the actual optimization
+    // occurs, Ceres performs a number of preprocessing steps. These
+    // include error checks, memory allocations, and reorderings. This
+    // time is accounted for as preprocessing time.
     double preprocessor_time_in_seconds;
+
+    // Time spent in the TrustRegionMinimizer.
     double minimizer_time_in_seconds;
+
+    // After the Minimizer is finished, some time is spent in
+    // re-evaluating residuals etc. This time is accounted for in the
+    // postprocessor time.
+    double postprocessor_time_in_seconds;
+
+    // Some total of all time spent inside Ceres when Solve is called.
     double total_time_in_seconds;
 
     // Preprocessor summary.
diff --git a/include/ceres/types.h b/include/ceres/types.h
index 705097f..0dcb354 100644
--- a/include/ceres/types.h
+++ b/include/ceres/types.h
@@ -158,8 +158,29 @@
   PER_MINIMIZER_ITERATION
 };
 
+// Ceres supports different strategies for computing the trust region
+// step.
 enum TrustRegionStrategyType {
+  // The default trust region strategy is to use the step computation
+  // used in the Levenberg-Marquardt algorithm. For more details see
+  // levenberg_marquardt_strategy.h
   LEVENBERG_MARQUARDT,
+
+  // Powell's dogleg algorithm interpolates between the Cauchy point
+  // and the Gauss-Newton step. It is particularly useful if the
+  // LEVENBERG_MARQUARDT algorithm is making a large number of
+  // unsuccessful steps. For more details see dogleg_strategy.h.
+  //
+  // NOTES:
+  //
+  // 1. This strategy has not been experimented with or tested as
+  // extensively as LEVENBERG_MARQUARDT, and therefore it should be
+  // considered EXPERIMENTAL for now.
+  //
+  // 2. For now this strategy should only be used with exact
+  // factorization based linear solvers, i.e., SPARSE_SCHUR,
+  // DENSE_SCHUR, DENSE_QR and SPARSE_NORMAL_CHOLESKY.
+  DOGLEG
 };
 
 enum SolverTerminationType {
@@ -261,7 +282,9 @@
     LinearSolverTerminationType type);
 const char* OrderingTypeToString(OrderingType type);
 const char* SolverTerminationTypeToString(SolverTerminationType type);
-
+const char* SparseLinearAlgebraLibraryTypeToString(
+    SparseLinearAlgebraLibraryType type);
+const char* TrustRegionStrategyTypeToString( TrustRegionStrategyType type);
 bool IsSchurType(LinearSolverType type);
 
 }  // namespace ceres