// Ceres Solver - A fast non-linear least squares minimizer

// Copyright 2015 Google Inc. All rights reserved.

// http://ceres-solver.org/

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// Author: keir@google.com (Keir Mierle)

#include "ceres/scratch_evaluate_preparer.h"

#include "ceres/parameter_block.h"

#include "ceres/program.h"

#include "ceres/residual_block.h"

namespace ceres {

namespace internal {

ScratchEvaluatePreparer* ScratchEvaluatePreparer::Create(

    const Program &program,

    int num_threads) {

  ScratchEvaluatePreparer* preparers = new ScratchEvaluatePreparer[num_threads];

  int max_derivatives_per_residual_block =

      program.MaxDerivativesPerResidualBlock();

  for (int i = 0; i < num_threads; i++) {

    preparers[i].Init(max_derivatives_per_residual_block);

  }

  return preparers;

}

void ScratchEvaluatePreparer::Init(int max_derivatives_per_residual_block) {

  jacobian_scratch_.reset(

      new double[max_derivatives_per_residual_block]);

}

// Point the jacobian blocks into the scratch area of this evaluate preparer.

void ScratchEvaluatePreparer::Prepare(const ResidualBlock* residual_block,

                                      int /* residual_block_index */,

                                      SparseMatrix* /* jacobian */,

                                      double** jacobians) {

  double* jacobian_block_cursor = jacobian_scratch_.get();

  int num_residuals = residual_block->NumResiduals();

  int num_parameter_blocks = residual_block->NumParameterBlocks();

  for (int j = 0; j < num_parameter_blocks; ++j) {

    const ParameterBlock* parameter_block =

        residual_block->parameter_blocks()[j];

    if (parameter_block->IsConstant()) {

      jacobians[j] = NULL;

    } else {

      jacobians[j] = jacobian_block_cursor;

      jacobian_block_cursor += num_residuals * parameter_block->LocalSize();

    }

  }

}

}  // namespace internal

}  // namespace ceres