dgetrf.c

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/* DGETRF.F -- translated by f2c (version 19941215).
   You must link the resulting object file with the libraries:
        -lf2c -lm   (in that order)
*/

#include "f2c.h"

/* Table of constant values */

static integer c__1 = 1;
static integer c_n1 = -1;
static doublereal c_b16 = 1.;
static doublereal c_b19 = -1.;

/* Subroutine */ int dgetrf_(m, n, a, lda, ipiv, info)
integer *m, *n;
doublereal *a;
integer *lda, *ipiv, *info;
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3, i__4, i__5;

    /* Local variables */
    static integer i, j;
    extern /* Subroutine */ int dgemm_();
    static integer iinfo;
    extern /* Subroutine */ int dtrsm_(), dgetf2_();
    static integer jb, nb;
    extern /* Subroutine */ int xerbla_();
    extern integer ilaenv_();
    extern /* Subroutine */ int dlaswp_();


/*  -- LAPACK routine (version 1.1) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/*     Courant Institute, Argonne National Lab, and Rice University */
/*     March 31, 1993 */

/*     .. 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. */

/*  ===================================================================== 
*/

/*     .. Parameters .. */
/*     .. */
/*     .. Local Scalars .. */
/*     .. */
/*     .. External Subroutines .. */
/*     .. */
/*     .. External Functions .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Executable Statements .. */

/*     Test the input parameters. */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = a_dim1 + 1;
    a -= a_offset;
    --ipiv;

    /* Function Body */
    *info = 0;
    if (*m < 0) {
        *info = -1;
    } else if (*n < 0) {
        *info = -2;
    } else if (*lda < max(1,*m)) {
        *info = -4;
    }
    if (*info != 0) {
        i__1 = -(*info);
        xerbla_("DGETRF", &i__1, 6L);
        return 0;
    }

/*     Quick return if possible */

    if (*m == 0 || *n == 0) {
        return 0;
    }

/*     Determine the block size for this environment. */

    nb = ilaenv_(&c__1, "DGETRF", " ", m, n, &c_n1, &c_n1, 6L, 1L);
    if (nb <= 1 || nb >= min(*m,*n)) {

/*        Use unblocked code. */

        dgetf2_(m, n, &a[a_offset], lda, &ipiv[1], info);
    } else {

/*        Use blocked code. */

        i__1 = min(*m,*n);
        i__2 = nb;
        for (j = 1; i__2 < 0 ? j >= i__1 : j <= i__1; j += i__2) {
/* Computing MIN */
            i__3 = min(*m,*n) - j + 1;
            jb = min(i__3,nb);

/*           Factor diagonal and subdiagonal blocks and test for e
xact */
/*           singularity. */

            i__3 = *m - j + 1;
            dgetf2_(&i__3, &jb, &a[j + j * a_dim1], lda, &ipiv[j], &iinfo);

/*           Adjust INFO and the pivot indices. */

            if (*info == 0 && iinfo > 0) {
                *info = iinfo + j - 1;
            }
/* Computing MIN */
            i__4 = *m, i__5 = j + jb - 1;
            i__3 = min(i__4,i__5);
            for (i = j; i <= i__3; ++i) {
                ipiv[i] = j - 1 + ipiv[i];
/* L10: */
            }

/*           Apply interchanges to columns 1:J-1. */

            i__3 = j - 1;
            i__4 = j + jb - 1;
            dlaswp_(&i__3, &a[a_offset], lda, &j, &i__4, &ipiv[1], &c__1);

            if (j + jb <= *n) {

/*              Apply interchanges to columns J+JB:N. */

                i__3 = *n - j - jb + 1;
                i__4 = j + jb - 1;
                dlaswp_(&i__3, &a[(j + jb) * a_dim1 + 1], lda, &j, &i__4, &
                        ipiv[1], &c__1);

/*              Compute block row of U. */

                i__3 = *n - j - jb + 1;
                dtrsm_("Left", "Lower", "No transpose", "Unit", &jb, &i__3, &
                        c_b16, &a[j + j * a_dim1], lda, &a[j + (j + jb) * 
                        a_dim1], lda, 4L, 5L, 12L, 4L);
                if (j + jb <= *m) {

/*                 Update trailing submatrix. */

                    i__3 = *m - j - jb + 1;
                    i__4 = *n - j - jb + 1;
                    dgemm_("No transpose", "No transpose", &i__3, &i__4, &jb, 
                            &c_b19, &a[j + jb + j * a_dim1], lda, &a[j + (j + 
                            jb) * a_dim1], lda, &c_b16, &a[j + jb + (j + jb) *
                             a_dim1], lda, 12L, 12L);
                }
            }
/* L20: */
        }
    }
    return 0;

/*     End of DGETRF */

} /* dgetrf_ */

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