dlib C++ Library - getrf.h

    // Copyright (C) 2010  Davis E. King (davis@dlib.net)
    // License: Boost Software License   See LICENSE.txt for the full license.
    #ifndef DLIB_LAPACk_GETRF_Hh_
    #define DLIB_LAPACk_GETRF_Hh_

    #include "fortran_id.h"
    #include "../matrix.h"

    namespace dlib
    {
        namespace lapack
        {
            namespace binding
            {
                extern "C"
                {
                    void DLIB_FORTRAN_ID(dgetrf) (const integer *m, const integer *n, double *a,
                                                  const integer *lda, integer *ipiv, integer *info);

                    void DLIB_FORTRAN_ID(sgetrf) (const integer *m, const integer *n, float *a,
                                                  const integer *lda, integer *ipiv, integer *info);

                }

                inline int getrf (integer m, integer n, double *a,
                                  integer lda, integer *ipiv)
                {
                    integer info = 0;
                    DLIB_FORTRAN_ID(dgetrf)(&m, &n, a, &lda, ipiv, &info);
                    return info;
                }

                inline int getrf (integer m, integer n, float *a,
                                  integer lda, integer *ipiv)
                {
                    integer info = 0;
                    DLIB_FORTRAN_ID(sgetrf)(&m, &n, a, &lda, ipiv, &info);
                    return info;
                }

            }

        // ------------------------------------------------------------------------------------

    /*  -- LAPACK routine (version 3.1) -- */
    /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
    /*     November 2006 */

    /*     .. Scalar Arguments .. */
    /*     .. */
    /*     .. Array Arguments .. */
    /*     .. */

    /*  Purpose */
    /*  ======= */

    /*  DGETRF computes an LU factorization of a general M-by-N matrix A */
    /*  using partial pivoting with row interchanges. */

    /*  The factorization has the form */
    /*     A = P * L * U */
    /*  where P is a permutation matrix, L is lower triangular with unit */
    /*  diagonal elements (lower trapezoidal if m > n), and U is upper */
    /*  triangular (upper trapezoidal if m < n). */

    /*  This is the right-looking Level 3 BLAS version of the algorithm. */

    /*  Arguments */
    /*  ========= */

    /*  M       (input) INTEGER */
    /*          The number of rows of the matrix A.  M >= 0. */

    /*  N       (input) INTEGER */
    /*          The number of columns of the matrix A.  N >= 0. */

    /*  A       (input/output) DOUBLE PRECISION array, dimension (LDA,N) */
    /*          On entry, the M-by-N matrix to be factored. */
    /*          On exit, the factors L and U from the factorization */
    /*          A = P*L*U; the unit diagonal elements of L are not stored. */

    /*  LDA     (input) INTEGER */
    /*          The leading dimension of the array A.  LDA >= max(1,M). */

    /*  IPIV    (output) INTEGER array, dimension (min(M,N)) */
    /*          The pivot indices; for 1 <= i <= min(M,N), row i of the */
    /*          matrix was interchanged with row IPIV(i). */

    /*  INFO    (output) INTEGER */
    /*          = 0:  successful exit */
    /*          < 0:  if INFO = -i, the i-th argument had an illegal value */
    /*          > 0:  if INFO = i, U(i,i) is exactly zero. The factorization */
    /*                has been completed, but the factor U is exactly */
    /*                singular, and division by zero will occur if it is used */
    /*                to solve a system of equations. */

        // ------------------------------------------------------------------------------------

            template <
                typename T,
                long NR1, long NR2,
                long NC1, long NC2,
                typename MM,
                typename layout
                >
            int getrf (
                matrix<T,NR1,NC1,MM,column_major_layout>& a,
                matrix<integer,NR2,NC2,MM,layout>& ipiv
            )
            {
                const long m = a.nr();
                const long n = a.nc();

                ipiv.set_size(std::min(m,n), 1);

                // compute the actual decomposition
                return binding::getrf(m, n, &a(0,0), a.nr(), &ipiv(0,0));
            }

        // ------------------------------------------------------------------------------------

        }

    }

    // ----------------------------------------------------------------------------------------

    #endif // DLIB_LAPACk_GETRF_Hh_