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/* ../../../dependencies/lapack/src/slartg.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"
/* Subroutine */ int slartg_(real *f, real *g, real *cs, real *sn, real *r__)
{
/* Initialized data */
static logical first = TRUE_;
/* System generated locals */
integer i__1;
real r__1, r__2;
/* Builtin functions */
double log(doublereal), pow_ri(real *, integer *), sqrt(doublereal);
/* Local variables */
static integer i__;
static real f1, g1, eps, scale;
static integer count;
static real safmn2, safmx2;
extern doublereal slamch_(char *, ftnlen);
static real safmin;
/* -- LAPACK auxiliary routine (version 3.0) -- */
/* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/* Courant Institute, Argonne National Lab, and Rice University */
/* September 30, 1994 */
/* .. Scalar Arguments .. */
/* .. */
/* Purpose */
/* ======= */
/* SLARTG generate a plane rotation so that */
/* [ CS SN ] . [ F ] = [ R ] where CS**2 + SN**2 = 1. */
/* [ -SN CS ] [ G ] [ 0 ] */
/* This is a slower, more accurate version of the BLAS1 routine SROTG, */
/* with the following other differences: */
/* F and G are unchanged on return. */
/* If G=0, then CS=1 and SN=0. */
/* If F=0 and (G .ne. 0), then CS=0 and SN=1 without doing any */
/* floating point operations (saves work in SBDSQR when */
/* there are zeros on the diagonal). */
/* If F exceeds G in magnitude, CS will be positive. */
/* Arguments */
/* ========= */
/* F (input) REAL */
/* The first component of vector to be rotated. */
/* G (input) REAL */
/* The second component of vector to be rotated. */
/* CS (output) REAL */
/* The cosine of the rotation. */
/* SN (output) REAL */
/* The sine of the rotation. */
/* R (output) REAL */
/* The nonzero component of the rotated vector. */
/* ===================================================================== */
/* .. Parameters .. */
/* .. */
/* .. Local Scalars .. */
/* .. */
/* .. External Functions .. */
/* .. */
/* .. Intrinsic Functions .. */
/* .. */
/* .. Save statement .. */
/* .. */
/* .. Data statements .. */
/* .. */
/* .. Executable Statements .. */
if (first) {
first = FALSE_;
safmin = slamch_("S", (ftnlen)1);
eps = slamch_("E", (ftnlen)1);
r__1 = slamch_("B", (ftnlen)1);
i__1 = (integer) (log(safmin / eps) / log(slamch_("B", (ftnlen)1)) /
2.f);
safmn2 = pow_ri(&r__1, &i__1);
safmx2 = 1.f / safmn2;
}
if (*g == 0.f) {
*cs = 1.f;
*sn = 0.f;
*r__ = *f;
} else if (*f == 0.f) {
*cs = 0.f;
*sn = 1.f;
*r__ = *g;
} else {
f1 = *f;
g1 = *g;
/* Computing MAX */
r__1 = dabs(f1), r__2 = dabs(g1);
scale = dmax(r__1,r__2);
if (scale >= safmx2) {
count = 0;
L10:
++count;
f1 *= safmn2;
g1 *= safmn2;
/* Computing MAX */
r__1 = dabs(f1), r__2 = dabs(g1);
scale = dmax(r__1,r__2);
if (scale >= safmx2) {
goto L10;
}
/* Computing 2nd power */
r__1 = f1;
/* Computing 2nd power */
r__2 = g1;
*r__ = sqrt(r__1 * r__1 + r__2 * r__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
i__1 = count;
for (i__ = 1; i__ <= i__1; ++i__) {
*r__ *= safmx2;
/* L20: */
}
} else if (scale <= safmn2) {
count = 0;
L30:
++count;
f1 *= safmx2;
g1 *= safmx2;
/* Computing MAX */
r__1 = dabs(f1), r__2 = dabs(g1);
scale = dmax(r__1,r__2);
if (scale <= safmn2) {
goto L30;
}
/* Computing 2nd power */
r__1 = f1;
/* Computing 2nd power */
r__2 = g1;
*r__ = sqrt(r__1 * r__1 + r__2 * r__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
i__1 = count;
for (i__ = 1; i__ <= i__1; ++i__) {
*r__ *= safmn2;
/* L40: */
}
} else {
/* Computing 2nd power */
r__1 = f1;
/* Computing 2nd power */
r__2 = g1;
*r__ = sqrt(r__1 * r__1 + r__2 * r__2);
*cs = f1 / *r__;
*sn = g1 / *r__;
}
if (dabs(*f) > dabs(*g) && *cs < 0.f) {
*cs = -(*cs);
*sn = -(*sn);
*r__ = -(*r__);
}
}
return 0;
/* End of SLARTG */
} /* slartg_ */
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