Fix some clang-tidy warnings.

Change-Id: Ic71bf0fc561edc22e3051d156fac630fcfea5d92

internal/ceres/reorder_program_test.cc

diff --git a/internal/ceres/reorder_program_test.cc b/internal/ceres/reorder_program_test.cc
index a3e2c78..f7f67aa 100644
--- a/internal/ceres/reorder_program_test.cc
+++ b/internal/ceres/reorder_program_test.cc
@@ -70,12 +70,12 @@
   problem.AddParameterBlock(&y, 1);
   problem.AddParameterBlock(&z, 1);
 
-  problem.AddResidualBlock(new UnaryCostFunction(), NULL, &x);
-  problem.AddResidualBlock(new BinaryCostFunction(), NULL, &z, &x);
-  problem.AddResidualBlock(new BinaryCostFunction(), NULL, &z, &y);
-  problem.AddResidualBlock(new UnaryCostFunction(), NULL, &z);
-  problem.AddResidualBlock(new BinaryCostFunction(), NULL, &x, &y);
-  problem.AddResidualBlock(new UnaryCostFunction(), NULL, &y);
+  problem.AddResidualBlock(new UnaryCostFunction(), nullptr, &x);
+  problem.AddResidualBlock(new BinaryCostFunction(), nullptr, &z, &x);
+  problem.AddResidualBlock(new BinaryCostFunction(), nullptr, &z, &y);
+  problem.AddResidualBlock(new UnaryCostFunction(), nullptr, &z);
+  problem.AddResidualBlock(new BinaryCostFunction(), nullptr, &x, &y);
+  problem.AddResidualBlock(new UnaryCostFunction(), nullptr, &y);
 
   ParameterBlockOrdering* linear_solver_ordering = new ParameterBlockOrdering;
   linear_solver_ordering->AddElementToGroup(&x, 0);
@@ -173,12 +173,12 @@
       public ::testing::Test {
  protected:
   void SetUp() {
-    problem_.AddResidualBlock(new UnaryCostFunction(), NULL, &x_);
-    problem_.AddResidualBlock(new BinaryCostFunction(), NULL, &z_, &x_);
-    problem_.AddResidualBlock(new BinaryCostFunction(), NULL, &z_, &y_);
-    problem_.AddResidualBlock(new UnaryCostFunction(), NULL, &z_);
-    problem_.AddResidualBlock(new BinaryCostFunction(), NULL, &x_, &y_);
-    problem_.AddResidualBlock(new UnaryCostFunction(), NULL, &y_);
+    problem_.AddResidualBlock(new UnaryCostFunction(), nullptr, &x_);
+    problem_.AddResidualBlock(new BinaryCostFunction(), nullptr, &z_, &x_);
+    problem_.AddResidualBlock(new BinaryCostFunction(), nullptr, &z_, &y_);
+    problem_.AddResidualBlock(new UnaryCostFunction(), nullptr, &z_);
+    problem_.AddResidualBlock(new BinaryCostFunction(), nullptr, &x_, &y_);
+    problem_.AddResidualBlock(new UnaryCostFunction(), nullptr, &y_);
   }
 
   void ComputeAndValidateOrdering(
@@ -260,12 +260,12 @@
   problem.AddParameterBlock(&y, 1);
   problem.AddParameterBlock(&z, 1);
 
-  problem.AddResidualBlock(new UnaryCostFunction(), NULL, &x);
-  problem.AddResidualBlock(new BinaryCostFunction(), NULL, &z, &x);
-  problem.AddResidualBlock(new BinaryCostFunction(), NULL, &z, &y);
-  problem.AddResidualBlock(new UnaryCostFunction(), NULL, &z);
-  problem.AddResidualBlock(new BinaryCostFunction(), NULL, &x, &y);
-  problem.AddResidualBlock(new UnaryCostFunction(), NULL, &y);
+  problem.AddResidualBlock(new UnaryCostFunction(), nullptr, &x);
+  problem.AddResidualBlock(new BinaryCostFunction(), nullptr, &z, &x);
+  problem.AddResidualBlock(new BinaryCostFunction(), nullptr, &z, &y);
+  problem.AddResidualBlock(new UnaryCostFunction(), nullptr, &z);
+  problem.AddResidualBlock(new BinaryCostFunction(), nullptr, &x, &y);
+  problem.AddResidualBlock(new UnaryCostFunction(), nullptr, &y);
 
   std::vector<ResidualBlockId> residual_block_ids;
   problem.GetResidualBlocks(&residual_block_ids);

internal/ceres/solver.cc

diff --git a/internal/ceres/solver.cc b/internal/ceres/solver.cc
index b22a5e1..861d8d3 100644
--- a/internal/ceres/solver.cc
+++ b/internal/ceres/solver.cc
@@ -198,7 +198,7 @@
     }
   }
 
-  if (options.trust_region_minimizer_iterations_to_dump.size() > 0 &&
+  if (!options.trust_region_minimizer_iterations_to_dump.empty() &&
       options.trust_region_problem_dump_format_type != CONSOLE &&
       options.trust_region_problem_dump_directory.empty()) {
     *error = "Solver::Options::trust_region_problem_dump_directory is empty.";
@@ -219,7 +219,7 @@
 
   if (options.linear_solver_type == CGNR &&
       options.preconditioner_type == SUBSET &&
-      options.residual_blocks_for_subset_preconditioner.size() == 0) {
+      options.residual_blocks_for_subset_preconditioner.empty()) {
     *error =
         "When using SUBSET preconditioner, "
         "Solver::Options::residual_blocks_for_subset_preconditioner cannot be "
@@ -285,7 +285,7 @@
 #undef OPTION_LT_OPTION
 
 void StringifyOrdering(const vector<int>& ordering, string* report) {
-  if (ordering.size() == 0) {
+  if (ordering.empty()) {
     internal::StringAppendF(report, "AUTOMATIC");
     return;
   }

internal/ceres/trust_region_preprocessor.cc

diff --git a/internal/ceres/trust_region_preprocessor.cc b/internal/ceres/trust_region_preprocessor.cc
index 498752b..65dee8a 100644
--- a/internal/ceres/trust_region_preprocessor.cc
+++ b/internal/ceres/trust_region_preprocessor.cc
@@ -251,7 +251,7 @@
   }
 
   pp->linear_solver.reset(LinearSolver::Create(pp->linear_solver_options));
-  return (pp->linear_solver.get() != nullptr);
+  return (pp->linear_solver != nullptr);
 }
 
 // Configure and create the evaluator.
@@ -277,7 +277,7 @@
                                         pp->reduced_program.get(),
                                         &pp->error));
 
-  return (pp->evaluator.get() != nullptr);
+  return (pp->evaluator != nullptr);
 }
 
 // If the user requested inner iterations, then find an inner
@@ -303,7 +303,7 @@
     return true;
   }
 
-  if (options.inner_iteration_ordering.get() != nullptr) {
+  if (options.inner_iteration_ordering != nullptr) {
     // If the user supplied an ordering, then remove the set of
     // inactive parameter blocks from it
     options.inner_iteration_ordering->Remove(pp->removed_parameter_blocks);