// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2017 Google Inc. All rights reserved.
// http://ceres-solver.org/
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#include "ceres/eigensparse.h"

#ifdef CERES_USE_EIGEN_SPARSE

#include <sstream>
#include "Eigen/SparseCholesky"
#include "Eigen/SparseCore"
#include "ceres/compressed_row_sparse_matrix.h"
#include "ceres/linear_solver.h"

namespace ceres {
namespace internal {

template <typename Solver>
class EigenSparseCholeskyTemplate : public SparseCholesky {
 public:
  EigenSparseCholeskyTemplate() : analyzed_(false) {}
  virtual ~EigenSparseCholeskyTemplate() {}
  virtual CompressedRowSparseMatrix::StorageType StorageType() const {
    return CompressedRowSparseMatrix::LOWER_TRIANGULAR;
  }

  virtual LinearSolverTerminationType Factorize(
      const Eigen::SparseMatrix<typename Solver::Scalar>& lhs,
      std::string* message) {
    if (!analyzed_) {
      solver_.analyzePattern(lhs);

      if (VLOG_IS_ON(2)) {
        std::stringstream ss;
        solver_.dumpMemory(ss);
        VLOG(2) << "Symbolic Analysis\n" << ss.str();
      }

      if (solver_.info() != Eigen::Success) {
        *message = "Eigen failure. Unable to find symbolic factorization.";
        return LINEAR_SOLVER_FATAL_ERROR;
      }

      analyzed_ = true;
    }

    solver_.factorize(lhs);
    if (solver_.info() != Eigen::Success) {
      *message = "Eigen failure. Unable to find numeric factorization.";
      return LINEAR_SOLVER_FAILURE;
    }
    return LINEAR_SOLVER_SUCCESS;
  }

  virtual LinearSolverTerminationType Solve(const double* rhs_ptr,
                                            double* solution_ptr,
                                            std::string* message) {
    CHECK(analyzed_) << "Solve called without a call to Factorize first.";

    ConstVectorRef rhs(rhs_ptr, solver_.cols());
    VectorRef solution(solution_ptr, solver_.cols());

    // The two casts are needed if the Scalar in this class is not
    // double. For code simplicitly we are going to assume that Eigen
    // is smart enough to figure out that casting a double Vector to a
    // double Vector is a straight copy. If this turns into a
    // performance bottleneck (unlikely), we can revisit this.
    solution =
        solver_
        .solve(rhs.template cast<typename Solver::Scalar>())
        .template cast<double>();

    if (solver_.info() != Eigen::Success) {
      *message = "Eigen failure. Unable to do triangular solve.";
      return LINEAR_SOLVER_FAILURE;
    }
    return LINEAR_SOLVER_SUCCESS;
  }

  virtual LinearSolverTerminationType Factorize(CompressedRowSparseMatrix* lhs,
                                                std::string* message) {
    CHECK_EQ(lhs->storage_type(), StorageType());

    typename Solver::Scalar* values_ptr = NULL;
    if (std::is_same<typename Solver::Scalar, double>::value) {
      values_ptr =
          reinterpret_cast<typename Solver::Scalar*>(lhs->mutable_values());
    } else {
      // In the case where the scalar used in this class is not
      // double. In that case, make a copy of the values array in the
      // CompressedRowSparseMatrix and cast it to Scalar along the way.
      values_ = ConstVectorRef(lhs->values(), lhs->num_nonzeros())
                    .cast<typename Solver::Scalar>();
      values_ptr = values_.data();
    }

    Eigen::MappedSparseMatrix<typename Solver::Scalar, Eigen::ColMajor>
        eigen_lhs(lhs->num_rows(),
                  lhs->num_rows(),
                  lhs->num_nonzeros(),
                  lhs->mutable_rows(),
                  lhs->mutable_cols(),
                  values_ptr);
    return Factorize(eigen_lhs, message);
  }

 private:
  Eigen::Matrix<typename Solver::Scalar, Eigen::Dynamic, 1> values_;
  bool analyzed_;
  Solver solver_;
};

SparseCholesky* EigenSparseCholesky::Create(const OrderingType ordering_type) {
  // The preprocessor gymnastics here are dealing with the fact that
  // before version 3.2.2, Eigen did not support a third template
  // parameter to specify the ordering and it always defaults to AMD.
#if EIGEN_VERSION_AT_LEAST(3, 2, 2)
  typedef Eigen::SimplicialLDLT<Eigen::SparseMatrix<double>,
                                Eigen::Upper,
                                Eigen::AMDOrdering<int>>
      WithAMDOrdering;
  typedef Eigen::SimplicialLDLT<Eigen::SparseMatrix<double>,
                                Eigen::Upper,
                                Eigen::NaturalOrdering<int>>
      WithNaturalOrdering;
  if (ordering_type == AMD) {
    return new EigenSparseCholeskyTemplate<WithAMDOrdering>();
  } else {
    return new EigenSparseCholeskyTemplate<WithNaturalOrdering>();
  }
#else
  typedef Eigen::SimplicialLDLT<Eigen::SparseMatrix<double>, Eigen::Upper>
      WithAMDOrdering;
  return new EigenSparseCholeskyTemplate<WithAMDOrdering>();
#endif
}

EigenSparseCholesky::~EigenSparseCholesky() {}

SparseCholesky* FloatEigenSparseCholesky::Create(
    const OrderingType ordering_type) {
  // The preprocessor gymnastics here are dealing with the fact that
  // before version 3.2.2, Eigen did not support a third template
  // parameter to specify the ordering and it always defaults to AMD.
#if EIGEN_VERSION_AT_LEAST(3, 2, 2)
  typedef Eigen::SimplicialLDLT<Eigen::SparseMatrix<float>,
                                Eigen::Upper,
                                Eigen::AMDOrdering<int> >
      WithAMDOrdering;
  typedef Eigen::SimplicialLDLT<Eigen::SparseMatrix<float>,
                                Eigen::Upper,
                                Eigen::NaturalOrdering<int> >
      WithNaturalOrdering;
  if (ordering_type == AMD) {
    LOG(FATAL) << "We should not be doing this";
    return new EigenSparseCholeskyTemplate<WithAMDOrdering>();
  } else {
    return new EigenSparseCholeskyTemplate<WithNaturalOrdering>();
  }
#else
  typedef Eigen::SimplicialLDLT<Eigen::SparseMatrix<float>, Eigen::Upper>
      WithAMDOrdering;
  return new EigenSparseCholeskyTemplate<WithAMDOrdering>();
#endif
}

FloatEigenSparseCholesky::~FloatEigenSparseCholesky() {}

}  // namespace internal
}  // namespace ceres

#endif  // CERES_USE_EIGEN_SPARSE