Using const ints in jacobian writers

Change-Id: I90ebb1956a15eddad2758bed7acaf3a2b90ce7c3

internal/ceres/block_jacobian_writer.cc

diff --git a/internal/ceres/block_jacobian_writer.cc b/internal/ceres/block_jacobian_writer.cc
index 544e913..29fe688 100644
--- a/internal/ceres/block_jacobian_writer.cc
+++ b/internal/ceres/block_jacobian_writer.cc
@@ -139,7 +139,7 @@
 // makes the final Write() a nop.
 std::unique_ptr<BlockEvaluatePreparer[]>
 BlockJacobianWriter::CreateEvaluatePreparers(unsigned num_threads) {
-  int max_derivatives_per_residual_block =
+  const int max_derivatives_per_residual_block =
       program_->MaxDerivativesPerResidualBlock();
 
   auto preparers = std::make_unique<BlockEvaluatePreparer[]>(num_threads);

internal/ceres/compressed_row_jacobian_writer.cc

diff --git a/internal/ceres/compressed_row_jacobian_writer.cc b/internal/ceres/compressed_row_jacobian_writer.cc
index 7112554..14c5251 100644
--- a/internal/ceres/compressed_row_jacobian_writer.cc
+++ b/internal/ceres/compressed_row_jacobian_writer.cc
@@ -90,8 +90,8 @@
     const {
   const auto& residual_blocks = program_->residual_blocks();
 
-  int total_num_residuals = program_->NumResiduals();
-  int total_num_effective_parameters = program_->NumEffectiveParameters();
+  const int total_num_residuals = program_->NumResiduals();
+  const int total_num_effective_parameters = program_->NumEffectiveParameters();
 
   // Count the number of jacobian nonzeros.
   int num_jacobian_nonzeros = 0;

internal/ceres/dense_jacobian_writer.h

diff --git a/internal/ceres/dense_jacobian_writer.h b/internal/ceres/dense_jacobian_writer.h
index 0020937..82592bd 100644
--- a/internal/ceres/dense_jacobian_writer.h
+++ b/internal/ceres/dense_jacobian_writer.h
@@ -75,8 +75,8 @@
     DenseSparseMatrix* dense_jacobian = down_cast<DenseSparseMatrix*>(jacobian);
     const ResidualBlock* residual_block =
         program_->residual_blocks()[residual_id];
-    int num_parameter_blocks = residual_block->NumParameterBlocks();
-    int num_residuals = residual_block->NumResiduals();
+    const int num_parameter_blocks = residual_block->NumParameterBlocks();
+    const int num_residuals = residual_block->NumResiduals();
 
     // Now copy the jacobians for each parameter into the dense jacobian matrix.
     for (int j = 0; j < num_parameter_blocks; ++j) {