drotmg.c

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/* drotmg.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 drotmg_(doublereal *dd1, doublereal *dd2, doublereal *
        dx1, doublereal *dy1, doublereal *dparam)
{
    /* Initialized data */

    static doublereal zero = 0.;
    static doublereal one = 1.;
    static doublereal two = 2.;
    static doublereal gam = 4096.;
    static doublereal gamsq = 16777216.;
    static doublereal rgamsq = 5.9604645e-8;

    /* Format strings */
    static char fmt_120[] = "";
    static char fmt_150[] = "";
    static char fmt_180[] = "";
    static char fmt_210[] = "";

    /* System generated locals */
    doublereal d__1;

    /* Local variables */
    doublereal du, dp1, dp2, dq1, dq2, dh11, dh12, dh21, dh22;
    integer igo;
    doublereal dflag, dtemp;

    /* Assigned format variables */
    static char *igo_fmt;

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

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

/*     CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS */
/*     THE SECOND COMPONENT OF THE 2-VECTOR  (DSQRT(DD1)*DX1,DSQRT(DD2)* */
/*     DY2)**T. */
/*     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). */
/*     LOCATIONS 2-4 OF DPARAM CONTAIN DH11, DH21, DH12, AND DH22 */
/*     RESPECTIVELY. (VALUES OF 1.D0, -1.D0, OR 0.D0 IMPLIED BY THE */
/*     VALUE OF DPARAM(1) ARE NOT STORED IN DPARAM.) */

/*     THE VALUES OF GAMSQ AND RGAMSQ SET IN THE DATA STATEMENT MAY BE */
/*     INEXACT.  THIS IS OK AS THEY ARE ONLY USED FOR TESTING THE SIZE */
/*     OF DD1 AND DD2.  ALL ACTUAL SCALING OF DATA IS DONE USING GAM. */


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

/*  DD1    (input/output) DOUBLE PRECISION */

/*  DD2    (input/output) DOUBLE PRECISION */

/*  DX1    (input/output) DOUBLE PRECISION */

/*  DY1    (input) DOUBLE PRECISION */

/*  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 .. */
/*     .. */
/*     .. Intrinsic Functions .. */
/*     .. */
/*     .. Data statements .. */

    /* Parameter adjustments */
    --dparam;

    /* Function Body */
/*     .. */
    if (! (*dd1 < zero)) {
        goto L10;
    }
/*       GO ZERO-H-D-AND-DX1.. */
    goto L60;
L10:
/*     CASE-DD1-NONNEGATIVE */
    dp2 = *dd2 * *dy1;
    if (! (dp2 == zero)) {
        goto L20;
    }
    dflag = -two;
    goto L260;
/*     REGULAR-CASE.. */
L20:
    dp1 = *dd1 * *dx1;
    dq2 = dp2 * *dy1;
    dq1 = dp1 * *dx1;

    if (! (abs(dq1) > abs(dq2))) {
        goto L40;
    }
    dh21 = -(*dy1) / *dx1;
    dh12 = dp2 / dp1;

    du = one - dh12 * dh21;

    if (! (du <= zero)) {
        goto L30;
    }
/*         GO ZERO-H-D-AND-DX1.. */
    goto L60;
L30:
    dflag = zero;
    *dd1 /= du;
    *dd2 /= du;
    *dx1 *= du;
/*         GO SCALE-CHECK.. */
    goto L100;
L40:
    if (! (dq2 < zero)) {
        goto L50;
    }
/*         GO ZERO-H-D-AND-DX1.. */
    goto L60;
L50:
    dflag = one;
    dh11 = dp1 / dp2;
    dh22 = *dx1 / *dy1;
    du = one + dh11 * dh22;
    dtemp = *dd2 / du;
    *dd2 = *dd1 / du;
    *dd1 = dtemp;
    *dx1 = *dy1 * du;
/*         GO SCALE-CHECK */
    goto L100;
/*     PROCEDURE..ZERO-H-D-AND-DX1.. */
L60:
    dflag = -one;
    dh11 = zero;
    dh12 = zero;
    dh21 = zero;
    dh22 = zero;

    *dd1 = zero;
    *dd2 = zero;
    *dx1 = zero;
/*         RETURN.. */
    goto L220;
/*     PROCEDURE..FIX-H.. */
L70:
    if (! (dflag >= zero)) {
        goto L90;
    }

    if (! (dflag == zero)) {
        goto L80;
    }
    dh11 = one;
    dh22 = one;
    dflag = -one;
    goto L90;
L80:
    dh21 = -one;
    dh12 = one;
    dflag = -one;
L90:
    switch (igo) {
        case 0: goto L120;
        case 1: goto L150;
        case 2: goto L180;
        case 3: goto L210;
    }
/*     PROCEDURE..SCALE-CHECK */
L100:
L110:
    if (! (*dd1 <= rgamsq)) {
        goto L130;
    }
    if (*dd1 == zero) {
        goto L160;
    }
    igo = 0;
    igo_fmt = fmt_120;
/*              FIX-H.. */
    goto L70;
L120:
/* Computing 2nd power */
    d__1 = gam;
    *dd1 *= d__1 * d__1;
    *dx1 /= gam;
    dh11 /= gam;
    dh12 /= gam;
    goto L110;
L130:
L140:
    if (! (*dd1 >= gamsq)) {
        goto L160;
    }
    igo = 1;
    igo_fmt = fmt_150;
/*              FIX-H.. */
    goto L70;
L150:
/* Computing 2nd power */
    d__1 = gam;
    *dd1 /= d__1 * d__1;
    *dx1 *= gam;
    dh11 *= gam;
    dh12 *= gam;
    goto L140;
L160:
L170:
    if (! (abs(*dd2) <= rgamsq)) {
        goto L190;
    }
    if (*dd2 == zero) {
        goto L220;
    }
    igo = 2;
    igo_fmt = fmt_180;
/*              FIX-H.. */
    goto L70;
L180:
/* Computing 2nd power */
    d__1 = gam;
    *dd2 *= d__1 * d__1;
    dh21 /= gam;
    dh22 /= gam;
    goto L170;
L190:
L200:
    if (! (abs(*dd2) >= gamsq)) {
        goto L220;
    }
    igo = 3;
    igo_fmt = fmt_210;
/*              FIX-H.. */
    goto L70;
L210:
/* Computing 2nd power */
    d__1 = gam;
    *dd2 /= d__1 * d__1;
    dh21 *= gam;
    dh22 *= gam;
    goto L200;
L220:
    if (dflag < 0.) {
        goto L250;
    } else if (dflag == 0) {
        goto L230;
    } else {
        goto L240;
    }
L230:
    dparam[3] = dh21;
    dparam[4] = dh12;
    goto L260;
L240:
    dparam[2] = dh11;
    dparam[5] = dh22;
    goto L260;
L250:
    dparam[2] = dh11;
    dparam[3] = dh21;
    dparam[4] = dh12;
    dparam[5] = dh22;
L260:
    dparam[1] = dflag;
    return 0;
} /* drotmg_ */