drotm.c

Go to the documentation of this file.

/* drotm.f -- translated by f2c (version 20100827).
   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 "datatypes.h"

/* Subroutine */ int drotm_(integer *n, doublereal *dx, integer *incx, 
        doublereal *dy, integer *incy, doublereal *dparam)
{
    /* Initialized data */

    static doublereal zero = 0.;
    static doublereal two = 2.;

    /* System generated locals */
    integer i__1, i__2;

    /* Local variables */
    integer i__;
    doublereal w, z__;
    integer kx, ky;
    doublereal dh11, dh12, dh21, dh22, dflag;
    integer nsteps;

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

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

/*     APPLY THE MODIFIED GIVENS TRANSFORMATION, H, TO THE 2 BY N MATRIX */

/*     (DX**T) , WHERE **T INDICATES TRANSPOSE. THE ELEMENTS OF DX ARE IN */
/*     (DY**T) */

/*     DX(LX+I*INCX), I = 0 TO N-1, WHERE LX = 1 IF INCX .GE. 0, ELSE */
/*     LX = (-INCX)*N, AND SIMILARLY FOR SY USING LY AND INCY. */
/*     WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS.. */

/*     DFLAG=-1.D0     DFLAG=0.D0        DFLAG=1.D0     DFLAG=-2.D0 */

/*       (DH11  DH12)    (1.D0  DH12)    (DH11  1.D0)    (1.D0  0.D0) */
/*     H=(          )    (          )    (          )    (          ) */
/*       (DH21  DH22),   (DH21  1.D0),   (-1.D0 DH22),   (0.D0  1.D0). */
/*     SEE DROTMG FOR A DESCRIPTION OF DATA STORAGE IN DPARAM. */

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

/*  N      (input) INTEGER */
/*         number of elements in input vector(s) */

/*  DX     (input/output) DOUBLE PRECISION array, dimension N */
/*         double precision vector with N elements */

/*  INCX   (input) INTEGER */
/*         storage spacing between elements of DX */

/*  DY     (input/output) DOUBLE PRECISION array, dimension N */
/*         double precision vector with N elements */

/*  INCY   (input) INTEGER */
/*         storage spacing between elements of DY */

/*  DPARAM (input/output)  DOUBLE PRECISION array, dimension 5 */
/*     DPARAM(1)=DFLAG */
/*     DPARAM(2)=DH11 */
/*     DPARAM(3)=DH21 */
/*     DPARAM(4)=DH12 */
/*     DPARAM(5)=DH22 */

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

/*     .. Local Scalars .. */
/*     .. */
/*     .. Data statements .. */
    /* Parameter adjustments */
    --dparam;
    --dy;
    --dx;

    /* Function Body */
/*     .. */

    dflag = dparam[1];
    if (*n <= 0 || dflag + two == zero) {
        goto L140;
    }
    if (! (*incx == *incy && *incx > 0)) {
        goto L70;
    }

    nsteps = *n * *incx;
    if (dflag < 0.) {
        goto L50;
    } else if (dflag == 0) {
        goto L10;
    } else {
        goto L30;
    }
L10:
    dh12 = dparam[4];
    dh21 = dparam[3];
    i__1 = nsteps;
    i__2 = *incx;
    for (i__ = 1; i__2 < 0 ? i__ >= i__1 : i__ <= i__1; i__ += i__2) {
        w = dx[i__];
        z__ = dy[i__];
        dx[i__] = w + z__ * dh12;
        dy[i__] = w * dh21 + z__;
/* L20: */
    }
    goto L140;
L30:
    dh11 = dparam[2];
    dh22 = dparam[5];
    i__2 = nsteps;
    i__1 = *incx;
    for (i__ = 1; i__1 < 0 ? i__ >= i__2 : i__ <= i__2; i__ += i__1) {
        w = dx[i__];
        z__ = dy[i__];
        dx[i__] = w * dh11 + z__;
        dy[i__] = -w + dh22 * z__;
/* L40: */
    }
    goto L140;
L50:
    dh11 = dparam[2];
    dh12 = dparam[4];
    dh21 = dparam[3];
    dh22 = dparam[5];
    i__1 = nsteps;
    i__2 = *incx;
    for (i__ = 1; i__2 < 0 ? i__ >= i__1 : i__ <= i__1; i__ += i__2) {
        w = dx[i__];
        z__ = dy[i__];
        dx[i__] = w * dh11 + z__ * dh12;
        dy[i__] = w * dh21 + z__ * dh22;
/* L60: */
    }
    goto L140;
L70:
    kx = 1;
    ky = 1;
    if (*incx < 0) {
        kx = (1 - *n) * *incx + 1;
    }
    if (*incy < 0) {
        ky = (1 - *n) * *incy + 1;
    }

    if (dflag < 0.) {
        goto L120;
    } else if (dflag == 0) {
        goto L80;
    } else {
        goto L100;
    }
L80:
    dh12 = dparam[4];
    dh21 = dparam[3];
    i__2 = *n;
    for (i__ = 1; i__ <= i__2; ++i__) {
        w = dx[kx];
        z__ = dy[ky];
        dx[kx] = w + z__ * dh12;
        dy[ky] = w * dh21 + z__;
        kx += *incx;
        ky += *incy;
/* L90: */
    }
    goto L140;
L100:
    dh11 = dparam[2];
    dh22 = dparam[5];
    i__2 = *n;
    for (i__ = 1; i__ <= i__2; ++i__) {
        w = dx[kx];
        z__ = dy[ky];
        dx[kx] = w * dh11 + z__;
        dy[ky] = -w + dh22 * z__;
        kx += *incx;
        ky += *incy;
/* L110: */
    }
    goto L140;
L120:
    dh11 = dparam[2];
    dh12 = dparam[4];
    dh21 = dparam[3];
    dh22 = dparam[5];
    i__2 = *n;
    for (i__ = 1; i__ <= i__2; ++i__) {
        w = dx[kx];
        z__ = dy[ky];
        dx[kx] = w * dh11 + z__ * dh12;
        dy[ky] = w * dh21 + z__ * dh22;
        kx += *incx;
        ky += *incy;
/* L130: */
    }
L140:
    return 0;
} /* drotm_ */