dlaqge.c

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

#include "f2c.h"

/* Subroutine */ int dlaqge_(m, n, a, lda, r, c, rowcnd, colcnd, amax, equed, 
        equed_len)
integer *m, *n;
doublereal *a;
integer *lda;
doublereal *r, *c, *rowcnd, *colcnd, *amax;
char *equed;
ftnlen equed_len;
{
    /* System generated locals */
    integer a_dim1, a_offset, i__1, i__2;

    /* Local variables */
    static integer i, j;
    static doublereal large, small, cj;
    extern doublereal dlamch_();


/*  -- LAPACK auxiliary routine (version 1.1) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/*     Courant Institute, Argonne National Lab, and Rice University */
/*     February 29, 1992 */

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

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

/*  DLAQGE equilibrates a general M by N matrix A using the row and */
/*  scaling factors in the vectors R and C. */

/*  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 A. */
/*          On exit, the equilibrated matrix.  See EQUED for the form of 
*/
/*          the equilibrated matrix. */

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

/*  R       (input) DOUBLE PRECISION array, dimension (M) */
/*          The row scale factors for A. */

/*  C       (input) DOUBLE PRECISION array, dimension (N) */
/*          The column scale factors for A. */

/*  ROWCND  (input) DOUBLE PRECISION */
/*          Ratio of the smallest R(i) to the largest R(i). */

/*  COLCND  (input) DOUBLE PRECISION */
/*          Ratio of the smallest C(i) to the largest C(i). */

/*  AMAX    (input) DOUBLE PRECISION */
/*          Absolute value of largest matrix entry. */

/*  EQUED   (output) CHARACTER*1 */
/*          Specifies the form of equilibration that was done. */
/*          = 'N':  No equilibration */
/*          = 'R':  Row equilibration, i.e., A has been premultiplied by 
*/
/*                  diag(R). */
/*          = 'C':  Column equilibration, i.e., A has been postmultiplied 
*/
/*                  by diag(C). */
/*          = 'B':  Both row and column equilibration, i.e., A has been */
/*                  replaced by diag(R) * A * diag(C). */

/*  Internal Parameters */
/*  =================== */

/*  THRESH is a threshold value used to decide if row or column scaling */
/*  should be done based on the ratio of the row or column scaling */
/*  factors.  If ROWCND < THRESH, row scaling is done, and if */
/*  COLCND < THRESH, column scaling is done. */

/*  LARGE and SMALL are threshold values used to decide if row scaling */
/*  should be done based on the absolute size of the largest matrix */
/*  element.  If AMAX > LARGE or AMAX < SMALL, row scaling is done. */

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

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

/*     Quick return if possible */

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

    /* Function Body */
    if (*m <= 0 || *n <= 0) {
        *(unsigned char *)equed = 'N';
        return 0;
    }

/*     Initialize LARGE and SMALL. */

    small = dlamch_("Safe minimum", 12L) / dlamch_("Precision", 9L);
    large = 1. / small;

    if (*rowcnd >= .1 && *amax >= small && *amax <= large) {

/*        No row scaling */

        if (*colcnd >= .1) {

/*           No column scaling */

            *(unsigned char *)equed = 'N';
        } else {

/*           Column scaling */

            i__1 = *n;
            for (j = 1; j <= i__1; ++j) {
                cj = c[j];
                i__2 = *m;
                for (i = 1; i <= i__2; ++i) {
                    a[i + j * a_dim1] = cj * a[i + j * a_dim1];
/* L10: */
                }
/* L20: */
            }
            *(unsigned char *)equed = 'C';
        }
    } else if (*colcnd >= .1) {

/*        Row scaling, no column scaling */

        i__1 = *n;
        for (j = 1; j <= i__1; ++j) {
            i__2 = *m;
            for (i = 1; i <= i__2; ++i) {
                a[i + j * a_dim1] = r[i] * a[i + j * a_dim1];
/* L30: */
            }
/* L40: */
        }
        *(unsigned char *)equed = 'R';
    } else {

/*        Row and column scaling */

        i__1 = *n;
        for (j = 1; j <= i__1; ++j) {
            cj = c[j];
            i__2 = *m;
            for (i = 1; i <= i__2; ++i) {
                a[i + j * a_dim1] = cj * r[i] * a[i + j * a_dim1];
/* L50: */
            }
/* L60: */
        }
        *(unsigned char *)equed = 'B';
    }

    return 0;

/*     End of DLAQGE */

} /* dlaqge_ */

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