/*  -- translated by f2c (version 20240504).
   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
*/

#include "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 )   

         INTEGER            INFO, LDA, M, N   
         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.   

   > \date September 2012   

   > \ingroup doubleGEcomputational   

    =====================================================================   
   Subroutine */ int igraphdgetf2_(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 igraphdger_(integer *, integer *, doublereal *, 
	    doublereal *, integer *, doublereal *, integer *, doublereal *, 
	    integer *), igraphdscal_(integer *, doublereal *, doublereal *, integer 
	    *);
    doublereal sfmin;
    extern /* Subroutine */ int igraphdswap_(integer *, doublereal *, integer *, 
	    doublereal *, integer *);
    extern doublereal igraphdlamch_(char *);
    extern integer igraphidamax_(integer *, doublereal *, integer *);
    extern /* Subroutine */ int igraphxerbla_(char *, integer *, ftnlen);


/*  -- LAPACK computational routine (version 3.4.2) --   
    -- LAPACK is a software package provided by Univ. of Tennessee,    --   
    -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--   
       September 2012   


    =====================================================================   


       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);
	igraphxerbla_("DGETF2", &i__1, (ftnlen)6);
	return 0;
    }

/*     Quick return if possible */

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

/*     Compute machine safe minimum */

    sfmin = igraphdlamch_("S");

    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 + igraphidamax_(&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) {
		igraphdswap_(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];
		    igraphdscal_(&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;
	    igraphdger_(&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 */

} /* igraphdgetf2_ */

