PartialPivLU_LAPACKE.h

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 ********************************************************************************
 *   Content : Eigen bindings to LAPACKe
 *     LU decomposition with partial pivoting based on LAPACKE_?getrf function.
 ********************************************************************************
*/
// SPDX-License-Identifier: BSD-3-Clause
 
#ifndef EIGEN_PARTIALLU_LAPACK_H
#define EIGEN_PARTIALLU_LAPACK_H
 
// IWYU pragma: private
#include "./InternalHeaderCheck.h"
 
namespace Eigen {
 
namespace internal {
 
namespace lapacke_helpers {
// -------------------------------------------------------------------------------------------------------------------
//        Generic lapacke partial lu implementation that converts arguments and dispatches to getrf
// -------------------------------------------------------------------------------------------------------------------
 
template <typename Scalar, int StorageOrder>
struct lapacke_partial_lu {
  static lapack_int blocked_lu(Index rows, Index cols, Scalar* lu_data, Index luStride, lapack_int* row_transpositions,
                               lapack_int& nb_transpositions, lapack_int maxBlockSize = 256) {
    // Set up parameters for getrf
    lapack_int matrix_order = StorageOrder == RowMajor ? LAPACK_ROW_MAJOR : LAPACK_COL_MAJOR;
    lapack_int lda = to_lapack(luStride);
    Scalar* a = lu_data;
    lapack_int* ipiv = row_transpositions;
    lapack_int m = to_lapack(rows);
    lapack_int n = to_lapack(cols);
    nb_transpositions = 0;
 
    lapack_int info = getrf(matrix_order, m, n, to_lapack(a), lda, ipiv);
    if (info == -4) {
      // High-level LAPACKE may reject NaN inputs before calling LAPACK. Eigen's native path preserves determinant
      // propagation for these values.
      return generic_partial_lu_impl<Scalar, StorageOrder, lapack_int, Dynamic>::blocked_lu(
          rows, cols, lu_data, luStride, row_transpositions, nb_transpositions, maxBlockSize);
    }
    eigen_assert(info >= 0);
 
    // getrf returns min(m, n) pivots.
    for (int i = 0; i < numext::mini(m, n); i++) {
      ipiv[i]--;
      if (ipiv[i] != i) nb_transpositions++;
    }
    lapack_int first_zero_pivot = info;
    return first_zero_pivot;
  }
};
}  // end namespace lapacke_helpers
 
/*
 * Here, we just put the generic implementation from lapacke_partial_lu into a partial specialization of the
 * partial_lu_impl type. This specialization is more specialized than the generic implementations that Eigen implements,
 * so if the Scalar type matches they will be chosen.
 */
#define EIGEN_LAPACKE_PARTIAL_LU(EIGTYPE)                            \
  template <int StorageOrder>                                        \
  struct partial_lu_impl<EIGTYPE, StorageOrder, lapack_int, Dynamic> \
      : public lapacke_helpers::lapacke_partial_lu<EIGTYPE, StorageOrder> {};
 
EIGEN_LAPACKE_PARTIAL_LU(double)
EIGEN_LAPACKE_PARTIAL_LU(float)
EIGEN_LAPACKE_PARTIAL_LU(std::complex<double>)
EIGEN_LAPACKE_PARTIAL_LU(std::complex<float>)
 
#undef EIGEN_LAPACKE_PARTIAL_LU
 
}  // end namespace internal
 
}  // end namespace Eigen
 
#endif  // EIGEN_PARTIALLU_LAPACK_H