// 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.
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//   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
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// POSSIBILITY OF SUCH DAMAGE.
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// Author: sameeragarwal@google.com (Sameer Agarwal)

#include "ceres/lapack.h"

#include "ceres/internal/port.h"
#include "ceres/linear_solver.h"
#include "glog/logging.h"

// C interface to the LAPACK Cholesky factorization and triangular solve.
extern "C" void dpotrf_(char* uplo,
                       int* n,
                       double* a,
                       int* lda,
                       int* info);

extern "C" void dpotrs_(char* uplo,
                        int* n,
                        int* nrhs,
                        double* a,
                        int* lda,
                        double* b,
                        int* ldb,
                        int* info);

extern "C" void dgels_(char* uplo,
                       int* m,
                       int* n,
                       int* nrhs,
                       double* a,
                       int* lda,
                       double* b,
                       int* ldb,
                       double* work,
                       int* lwork,
                       int* info);


namespace ceres {
namespace internal {

LinearSolverTerminationType LAPACK::SolveInPlaceUsingCholesky(
    int num_rows,
    const double* in_lhs,
    double* rhs_and_solution,
    std::string* message) {
#ifdef CERES_NO_LAPACK
  LOG(FATAL) << "Ceres was built without a BLAS library.";
  return LINEAR_SOLVER_FATAL_ERROR;
#else
  char uplo = 'L';
  int n = num_rows;
  int info = 0;
  int nrhs = 1;
  double* lhs = const_cast<double*>(in_lhs);

  dpotrf_(&uplo, &n, lhs, &n, &info);
  if (info < 0) {
    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
               << "Please report it."
               << "LAPACK::dpotrf fatal error."
               << "Argument: " << -info << " is invalid.";
    return LINEAR_SOLVER_FATAL_ERROR;
  }

  if (info > 0) {
    *message =
        StringPrintf(
            "LAPACK::dpotrf numerical failure. "
             "The leading minor of order %d is not positive definite.", info);
    return LINEAR_SOLVER_FAILURE;
  }

  dpotrs_(&uplo, &n, &nrhs, lhs, &n, rhs_and_solution, &n, &info);
  if (info < 0) {
    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
               << "Please report it."
               << "LAPACK::dpotrs fatal error."
               << "Argument: " << -info << " is invalid.";
    return LINEAR_SOLVER_FATAL_ERROR;
  }

  *message = "Success";
  return LINEAR_SOLVER_SUCCESS;
#endif
}

int LAPACK::EstimateWorkSizeForQR(int num_rows, int num_cols) {
#ifdef CERES_NO_LAPACK
  LOG(FATAL) << "Ceres was built without a LAPACK library.";
  return -1;
#else
  char trans = 'N';
  int nrhs = 1;
  int lwork = -1;
  double work;
  int info = 0;
  dgels_(&trans,
         &num_rows,
         &num_cols,
         &nrhs,
         NULL,
         &num_rows,
         NULL,
         &num_rows,
         &work,
         &lwork,
         &info);

  if (info < 0) {
    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
               << "Please report it."
               << "LAPACK::dgels fatal error."
               << "Argument: " << -info << " is invalid.";
  }
  return static_cast<int>(work);
#endif
}

LinearSolverTerminationType LAPACK::SolveInPlaceUsingQR(
    int num_rows,
    int num_cols,
    const double* in_lhs,
    int work_size,
    double* work,
    double* rhs_and_solution,
    std::string* message) {
#ifdef CERES_NO_LAPACK
  LOG(FATAL) << "Ceres was built without a LAPACK library.";
  return LINEAR_SOLVER_FATAL_ERROR;
#else
  char trans = 'N';
  int m = num_rows;
  int n = num_cols;
  int nrhs = 1;
  int lda = num_rows;
  int ldb = num_rows;
  int info = 0;
  double* lhs = const_cast<double*>(in_lhs);

  dgels_(&trans,
         &m,
         &n,
         &nrhs,
         lhs,
         &lda,
         rhs_and_solution,
         &ldb,
         work,
         &work_size,
         &info);

  if (info < 0) {
    LOG(FATAL) << "Congratulations, you found a bug in Ceres."
               << "Please report it."
               << "LAPACK::dgels fatal error."
               << "Argument: " << -info << " is invalid.";
  }

  *message = "Success.";
  return LINEAR_SOLVER_SUCCESS;
#endif
}

}  // namespace internal
}  // namespace ceres