idamax.c

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/* idamax.f -- translated by f2c (version 20061008).
   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"
#include "blaswrap.h"

integer idamax_(integer *n, doublereal *dx, integer *incx)
{
    /* System generated locals */
    integer ret_val, i__1;
    doublereal d__1;

    /* Local variables */
    integer i__, ix;
    doublereal dmax__;

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

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

/*     finds the index of element having max. absolute value. */
/*     jack dongarra, linpack, 3/11/78. */
/*     modified 3/93 to return if incx .le. 0. */
/*     modified 12/3/93, array(1) declarations changed to array(*) */


/*     .. Local Scalars .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
    /* Parameter adjustments */
    --dx;

    /* Function Body */
    ret_val = 0;
    if (*n < 1 || *incx <= 0) {
        return ret_val;
    }
    ret_val = 1;
    if (*n == 1) {
        return ret_val;
    }
    if (*incx == 1) {
        goto L20;
    }

/*        code for increment not equal to 1 */

    ix = 1;
    dmax__ = abs(dx[1]);
    ix += *incx;
    i__1 = *n;
    for (i__ = 2; i__ <= i__1; ++i__) {
        if ((d__1 = dx[ix], abs(d__1)) <= dmax__) {
            goto L5;
        }
        ret_val = i__;
        dmax__ = (d__1 = dx[ix], abs(d__1));
L5:
        ix += *incx;
/* L10: */
    }
    return ret_val;

/*        code for increment equal to 1 */

L20:
    dmax__ = abs(dx[1]);
    i__1 = *n;
    for (i__ = 2; i__ <= i__1; ++i__) {
        if ((d__1 = dx[i__], abs(d__1)) <= dmax__) {
            goto L30;
        }
        ret_val = i__;
        dmax__ = (d__1 = dx[i__], abs(d__1));
L30:
        ;
    }
    return ret_val;
} /* idamax_ */