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/* lapack/single/slartg.f -- translated by f2c (version 20050501).
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
*/
#ifdef __cplusplus
extern "C" {
#endif
#include "v3p_netlib.h"
/* Initialization function just calls the function once so that its
runtime-initialized constants are initialized. After the first
call it is safe to call the function from multiple threads at
once. */
void v3p_netlib_slartg_init()
{
real f=0, g=0, cs=0, sn=0, r=0;
slartg_(&f, &g, &cs, &sn, &r);
}
/*< SUBROUTINE SLARTG( F, G, CS, SN, R ) >*/
/* Subroutine */ int slartg_(real *f, real *g, real *cs, real *sn, real *r__)
{
/* Initialized data */
static logical first = TRUE_; /* runtime-initialized constant */
/* System generated locals */
integer i__1;
real r__1, r__2;
/* Builtin functions */
double log(doublereal), pow_ri(real *, integer *), sqrt(doublereal);
/* Local variables */
integer i__;
real f1, g1, eps, scale;
integer count;
static real safmn2, safmx2; /* runtime-initialized constant */
extern doublereal slamch_(char *, ftnlen);
static real safmin; /* runtime-initialized constant */
/* -- 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 .. */
/*< REAL CS, F, G, R, SN >*/
/* .. */
/* 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 .. */
/*< REAL ZERO >*/
/*< PARAMETER ( ZERO = 0.0E0 ) >*/
/*< REAL ONE >*/
/*< PARAMETER ( ONE = 1.0E0 ) >*/
/*< REAL TWO >*/
/*< PARAMETER ( TWO = 2.0E0 ) >*/
/* .. */
/* .. Local Scalars .. */
/*< LOGICAL FIRST >*/
/*< INTEGER COUNT, I >*/
/*< REAL EPS, F1, G1, SAFMIN, SAFMN2, SAFMX2, SCALE >*/
/* .. */
/* .. External Functions .. */
/*< REAL SLAMCH >*/
/*< EXTERNAL SLAMCH >*/
/* .. */
/* .. Intrinsic Functions .. */
/*< INTRINSIC ABS, INT, LOG, MAX, SQRT >*/
/* .. */
/* .. Save statement .. */
/*< SAVE FIRST, SAFMX2, SAFMIN, SAFMN2 >*/
/* .. */
/* .. Data statements .. */
/*< DATA FIRST / .TRUE. / >*/
/* .. */
/* .. Executable Statements .. */
/*< IF( FIRST ) THEN >*/
if (first) {
/*< FIRST = .FALSE. >*/
first = FALSE_;
/*< SAFMIN = SLAMCH( 'S' ) >*/
safmin = slamch_("S", (ftnlen)1);
/*< EPS = SLAMCH( 'E' ) >*/
eps = slamch_("E", (ftnlen)1);
/*< >*/
r__1 = slamch_("B", (ftnlen)1);
i__1 = (integer) (log(safmin / eps) / log(slamch_("B", (ftnlen)1)) / (
float)2.);
safmn2 = pow_ri(&r__1, &i__1);
/*< SAFMX2 = ONE / SAFMN2 >*/
safmx2 = (float)1. / safmn2;
/*< END IF >*/
}
/*< IF( G.EQ.ZERO ) THEN >*/
if (*g == (float)0.) {
/*< CS = ONE >*/
*cs = (float)1.;
/*< SN = ZERO >*/
*sn = (float)0.;
/*< R = F >*/
*r__ = *f;
/*< ELSE IF( F.EQ.ZERO ) THEN >*/
} else if (*f == (float)0.) {
/*< CS = ZERO >*/
*cs = (float)0.;
/*< SN = ONE >*/
*sn = (float)1.;
/*< R = G >*/
*r__ = *g;
/*< ELSE >*/
} else {
/*< F1 = F >*/
f1 = *f;
/*< G1 = G >*/
g1 = *g;
/*< SCALE = MAX( ABS( F1 ), ABS( G1 ) ) >*/
/* Computing MAX */
r__1 = dabs(f1), r__2 = dabs(g1);
scale = dmax(r__1,r__2);
/*< IF( SCALE.GE.SAFMX2 ) THEN >*/
if (scale >= safmx2) {
/*< COUNT = 0 >*/
count = 0;
/*< 10 CONTINUE >*/
L10:
/*< COUNT = COUNT + 1 >*/
++count;
/*< F1 = F1*SAFMN2 >*/
f1 *= safmn2;
/*< G1 = G1*SAFMN2 >*/
g1 *= safmn2;
/*< SCALE = MAX( ABS( F1 ), ABS( G1 ) ) >*/
/* Computing MAX */
r__1 = dabs(f1), r__2 = dabs(g1);
scale = dmax(r__1,r__2);
/*< >*/
if (scale >= safmx2) {
goto L10;
}
/*< R = SQRT( F1**2+G1**2 ) >*/
/* 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 >*/
*cs = f1 / *r__;
/*< SN = G1 / R >*/
*sn = g1 / *r__;
/*< DO 20 I = 1, COUNT >*/
i__1 = count;
for (i__ = 1; i__ <= i__1; ++i__) {
/*< R = R*SAFMX2 >*/
*r__ *= safmx2;
/*< 20 CONTINUE >*/
/* L20: */
}
/*< ELSE IF( SCALE.LE.SAFMN2 ) THEN >*/
} else if (scale <= safmn2) {
/*< COUNT = 0 >*/
count = 0;
/*< 30 CONTINUE >*/
L30:
/*< COUNT = COUNT + 1 >*/
++count;
/*< F1 = F1*SAFMX2 >*/
f1 *= safmx2;
/*< G1 = G1*SAFMX2 >*/
g1 *= safmx2;
/*< SCALE = MAX( ABS( F1 ), ABS( G1 ) ) >*/
/* Computing MAX */
r__1 = dabs(f1), r__2 = dabs(g1);
scale = dmax(r__1,r__2);
/*< >*/
if (scale <= safmn2) {
goto L30;
}
/*< R = SQRT( F1**2+G1**2 ) >*/
/* 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 >*/
*cs = f1 / *r__;
/*< SN = G1 / R >*/
*sn = g1 / *r__;
/*< DO 40 I = 1, COUNT >*/
i__1 = count;
for (i__ = 1; i__ <= i__1; ++i__) {
/*< R = R*SAFMN2 >*/
*r__ *= safmn2;
/*< 40 CONTINUE >*/
/* L40: */
}
/*< ELSE >*/
} else {
/*< R = SQRT( F1**2+G1**2 ) >*/
/* 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 >*/
*cs = f1 / *r__;
/*< SN = G1 / R >*/
*sn = g1 / *r__;
/*< END IF >*/
}
/*< IF( ABS( F ).GT.ABS( G ) .AND. CS.LT.ZERO ) THEN >*/
if (dabs(*f) > dabs(*g) && *cs < (float)0.) {
/*< CS = -CS >*/
*cs = -(*cs);
/*< SN = -SN >*/
*sn = -(*sn);
/*< R = -R >*/
*r__ = -(*r__);
/*< END IF >*/
}
/*< END IF >*/
}
/*< RETURN >*/
return 0;
/* End of SLARTG */
/*< END >*/
} /* slartg_ */
#ifdef __cplusplus
}
#endif
|
