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

// Copyright 2015 Google Inc. All rights reserved.

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

//

// Redistribution and use in source and binary forms, with or without

// modification, are permitted provided that the following conditions are met:

//

// * Redistributions of source code must retain the above copyright notice,

//   this list of conditions and the following disclaimer.

// * Redistributions in binary form must reproduce the above copyright notice,

//   this list of conditions and the following disclaimer in the documentation

//   and/or other materials provided with the distribution.

// * Neither the name of Google Inc. nor the names of its contributors may be

//   used to endorse or promote products derived from this software without

//   specific prior written permission.

//

// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE

// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

// POSSIBILITY OF SUCH DAMAGE.

//

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

#include "ceres/cgnr_solver.h"

#include "ceres/block_jacobi_preconditioner.h"

#include "ceres/cgnr_linear_operator.h"

#include "ceres/conjugate_gradients_solver.h"

#include "ceres/internal/eigen.h"

#include "ceres/linear_solver.h"

#include "ceres/wall_time.h"

#include "glog/logging.h"

namespace ceres {

namespace internal {

CgnrSolver::CgnrSolver(const LinearSolver::Options& options)

  : options_(options),

    preconditioner_(NULL) {

  if (options_.preconditioner_type != JACOBI &&

      options_.preconditioner_type != IDENTITY) {

    LOG(FATAL) << "CGNR only supports IDENTITY and JACOBI preconditioners.";

  }

}

LinearSolver::Summary CgnrSolver::SolveImpl(

    BlockSparseMatrix* A,

    const double* b,

    const LinearSolver::PerSolveOptions& per_solve_options,

    double* x) {

  EventLogger event_logger("CgnrSolver::Solve");

  // Form z = Atb.

  Vector z(A->num_cols());

  z.setZero();

  A->LeftMultiply(b, z.data());

  // Precondition if necessary.

  LinearSolver::PerSolveOptions cg_per_solve_options = per_solve_options;

  if (options_.preconditioner_type == JACOBI) {

    if (preconditioner_.get() == NULL) {

      preconditioner_.reset(new BlockJacobiPreconditioner(*A));

    }

    preconditioner_->Update(*A, per_solve_options.D);

    cg_per_solve_options.preconditioner = preconditioner_.get();

  }

  // Solve (AtA + DtD)x = z (= Atb).

  VectorRef(x, A->num_cols()).setZero();

  CgnrLinearOperator lhs(*A, per_solve_options.D);

  event_logger.AddEvent("Setup");

  ConjugateGradientsSolver conjugate_gradient_solver(options_);

  LinearSolver::Summary summary =

      conjugate_gradient_solver.Solve(&lhs, z.data(), cg_per_solve_options, x);

  event_logger.AddEvent("Solve");

  return summary;

}

}  // namespace internal

}  // namespace ceres