/* fortran/dgetf2.f -- translated by f2c (version 20200916).
   You must link the resulting object file with libf2c:
        on Microsoft Windows system, link with libf2c.lib;
        on Linux or Unix systems, link with .../path/to/libf2c.a -lm
        or, if you install libf2c.a in a standard place, with -lf2c -lm
        -- in that order, at the end of the command line, as in
                cc *.o -lf2c -lm
        Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,

                http://www.netlib.org/f2c/libf2c.zip
*/

#ifdef __cplusplus
extern "C" {
#endif
#include "lmp_f2c.h"

/* Table of constant values */

static integer c__1 = 1;
static doublereal c_b8 = -1.;

/* > \brief \b DGETF2 computes the LU factorization of a general m-by-n matrix using partial pivoting with row
 interchanges (unblocked algorithm). */

/*  =========== DOCUMENTATION =========== */

/* Online html documentation available at */
/*            http://www.netlib.org/lapack/explore-html/ */

/* > \htmlonly */
/* > Download DGETF2 + dependencies */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dgetf2.
f"> */
/* > [TGZ]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dgetf2.
f"> */
/* > [ZIP]</a> */
/* > <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dgetf2.
f"> */
/* > [TXT]</a> */
/* > \endhtmlonly */

/*  Definition: */
/*  =========== */

/*       SUBROUTINE DGETF2( M, N, A, LDA, IPIV, INFO ) */

/*       .. Scalar Arguments .. */
/*       INTEGER            INFO, LDA, M, N */
/*       .. */
/*       .. Array Arguments .. */
/*       INTEGER            IPIV( * ) */
/*       DOUBLE PRECISION   A( LDA, * ) */
/*       .. */


/* > \par Purpose: */
/*  ============= */
/* > */
/* > \verbatim */
/* > */
/* > DGETF2 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 2 BLAS version of the algorithm. */
/* > \endverbatim */

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

/* > \param[in] M */
/* > \verbatim */
/* >          M is INTEGER */
/* >          The number of rows of the matrix A.  M >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in] N */
/* > \verbatim */
/* >          N is INTEGER */
/* >          The number of columns of the matrix A.  N >= 0. */
/* > \endverbatim */
/* > */
/* > \param[in,out] A */
/* > \verbatim */
/* >          A is 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. */
/* > \endverbatim */
/* > */
/* > \param[in] LDA */
/* > \verbatim */
/* >          LDA is INTEGER */
/* >          The leading dimension of the array A.  LDA >= max(1,M). */
/* > \endverbatim */
/* > */
/* > \param[out] IPIV */
/* > \verbatim */
/* >          IPIV is 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). */
/* > \endverbatim */
/* > */
/* > \param[out] INFO */
/* > \verbatim */
/* >          INFO is INTEGER */
/* >          = 0: successful exit */
/* >          < 0: if INFO = -k, the k-th argument had an illegal value */
/* >          > 0: if INFO = k, U(k,k) 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. */
/* > \endverbatim */

/*  Authors: */
/*  ======== */

/* > \author Univ. of Tennessee */
/* > \author Univ. of California Berkeley */
/* > \author Univ. of Colorado Denver */
/* > \author NAG Ltd. */

/* > \ingroup doubleGEcomputational */

/*  ===================================================================== */
/* Subroutine */ int dgetf2_(integer *m, integer *n, doublereal *a, integer *
        lda, integer *ipiv, integer *info)
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2, i__3;
    doublereal d__1;

    /* Local variables */
    integer i__, j, jp;
    extern /* Subroutine */ int dger_(integer *, integer *, doublereal *,
            doublereal *, integer *, doublereal *, integer *, doublereal *,
            integer *), dscal_(integer *, doublereal *, doublereal *, integer
            *);
    doublereal sfmin;
    extern /* Subroutine */ int dswap_(integer *, doublereal *, integer *,
            doublereal *, integer *);
    extern doublereal dlamch_(char *, ftnlen);
    extern integer idamax_(integer *, doublereal *, integer *);
    extern /* Subroutine */ int xerbla_(char *, integer *, ftnlen);


/*  -- LAPACK computational routine -- */
/*  -- LAPACK is a software package provided by Univ. of Tennessee,    -- */
/*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- */

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

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

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

/*     Test the input parameters. */

    /* Parameter adjustments */
    a_dim1 = *lda;
    a_offset = 1 + a_dim1;
    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_((char *)"DGETF2", &i__1, (ftnlen)6);
        return 0;
    }

/*     Quick return if possible */

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

/*     Compute machine safe minimum */

    sfmin = dlamch_((char *)"S", (ftnlen)1);

    i__1 = min(*m,*n);
    for (j = 1; j <= i__1; ++j) {

/*        Find pivot and test for singularity. */

        i__2 = *m - j + 1;
        jp = j - 1 + idamax_(&i__2, &a[j + j * a_dim1], &c__1);
        ipiv[j] = jp;
        if (a[jp + j * a_dim1] != 0.) {

/*           Apply the interchange to columns 1:N. */

            if (jp != j) {
                dswap_(n, &a[j + a_dim1], lda, &a[jp + a_dim1], lda);
            }

/*           Compute elements J+1:M of J-th column. */

            if (j < *m) {
                if ((d__1 = a[j + j * a_dim1], abs(d__1)) >= sfmin) {
                    i__2 = *m - j;
                    d__1 = 1. / a[j + j * a_dim1];
                    dscal_(&i__2, &d__1, &a[j + 1 + j * a_dim1], &c__1);
                } else {
                    i__2 = *m - j;
                    for (i__ = 1; i__ <= i__2; ++i__) {
                        a[j + i__ + j * a_dim1] /= a[j + j * a_dim1];
/* L20: */
                    }
                }
            }

        } else if (*info == 0) {

            *info = j;
        }

        if (j < min(*m,*n)) {

/*           Update trailing submatrix. */

            i__2 = *m - j;
            i__3 = *n - j;
            dger_(&i__2, &i__3, &c_b8, &a[j + 1 + j * a_dim1], &c__1, &a[j + (
                    j + 1) * a_dim1], lda, &a[j + 1 + (j + 1) * a_dim1], lda);
        }
/* L10: */
    }
    return 0;

/*     End of DGETF2 */

} /* dgetf2_ */

#ifdef __cplusplus
        }
#endif