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/* blas/drotg.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"
/* Table of constant values */
static doublereal c_b4 = 1.;
/*< subroutine drotg(da,db,c,s) >*/
/* Subroutine */ int drotg_(doublereal *da, doublereal *db, doublereal *c__,
doublereal *s)
{
/* System generated locals */
doublereal d__1, d__2;
/* Builtin functions */
double sqrt(doublereal), d_sign(doublereal *, doublereal *);
/* Local variables */
doublereal r__, z__, roe, scale;
/* construct givens plane rotation. */
/* jack dongarra, linpack, 3/11/78. */
/*< double precision da,db,c,s,roe,scale,r,z >*/
/*< roe = db >*/
roe = *db;
/*< if( dabs(da) .gt. dabs(db) ) roe = da >*/
if (abs(*da) > abs(*db)) {
roe = *da;
}
/*< scale = dabs(da) + dabs(db) >*/
scale = abs(*da) + abs(*db);
/*< if( scale .ne. 0.0d0 ) go to 10 >*/
if (scale != 0.) {
goto L10;
}
/*< c = 1.0d0 >*/
*c__ = 1.;
/*< s = 0.0d0 >*/
*s = 0.;
/*< r = 0.0d0 >*/
r__ = 0.;
/*< z = 0.0d0 >*/
z__ = 0.;
/*< go to 20 >*/
goto L20;
/*< 10 r = scale*dsqrt((da/scale)**2 + (db/scale)**2) >*/
L10:
/* Computing 2nd power */
d__1 = *da / scale;
/* Computing 2nd power */
d__2 = *db / scale;
r__ = scale * sqrt(d__1 * d__1 + d__2 * d__2);
/*< r = dsign(1.0d0,roe)*r >*/
r__ = d_sign(&c_b4, &roe) * r__;
/*< c = da/r >*/
*c__ = *da / r__;
/*< s = db/r >*/
*s = *db / r__;
/*< z = 1.0d0 >*/
z__ = 1.;
/*< if( dabs(da) .gt. dabs(db) ) z = s >*/
if (abs(*da) > abs(*db)) {
z__ = *s;
}
/*< if( dabs(db) .ge. dabs(da) .and. c .ne. 0.0d0 ) z = 1.0d0/c >*/
if (abs(*db) >= abs(*da) && *c__ != 0.) {
z__ = 1. / *c__;
}
/*< 20 da = r >*/
L20:
*da = r__;
/*< db = z >*/
*db = z__;
/*< return >*/
return 0;
/*< end >*/
} /* drotg_ */
#ifdef __cplusplus
}
#endif
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