dlabad.c

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/* lapack/double/dlabad.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"

/*<       SUBROUTINE DLABAD( SMALL, LARGE ) >*/
/* Subroutine */ int dlabad_(doublereal *small, doublereal *large)
{
    /* Builtin functions */
    double d_lg10(doublereal *), sqrt(doublereal);


/*  -- LAPACK auxiliary routine (version 3.0) -- */
/*     Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., */
/*     Courant Institute, Argonne National Lab, and Rice University */
/*     October 31, 1992 */

/*     .. Scalar Arguments .. */
/*<       DOUBLE PRECISION   LARGE, SMALL >*/
/*     .. */

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

/*  DLABAD takes as input the values computed by DLAMCH for underflow and */
/*  overflow, and returns the square root of each of these values if the */
/*  log of LARGE is sufficiently large.  This subroutine is intended to */
/*  identify machines with a large exponent range, such as the Crays, and */
/*  redefine the underflow and overflow limits to be the square roots of */
/*  the values computed by DLAMCH.  This subroutine is needed because */
/*  DLAMCH does not compensate for poor arithmetic in the upper half of */
/*  the exponent range, as is found on a Cray. */

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

/*  SMALL   (input/output) DOUBLE PRECISION */
/*          On entry, the underflow threshold as computed by DLAMCH. */
/*          On exit, if LOG10(LARGE) is sufficiently large, the square */
/*          root of SMALL, otherwise unchanged. */

/*  LARGE   (input/output) DOUBLE PRECISION */
/*          On entry, the overflow threshold as computed by DLAMCH. */
/*          On exit, if LOG10(LARGE) is sufficiently large, the square */
/*          root of LARGE, otherwise unchanged. */

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

/*     .. Intrinsic Functions .. */
/*<       INTRINSIC          LOG10, SQRT >*/
/*     .. */
/*     .. Executable Statements .. */

/*     If it looks like we're on a Cray, take the square root of */
/*     SMALL and LARGE to avoid overflow and underflow problems. */

/*<       IF( LOG10( LARGE ).GT.2000.D0 ) THEN >*/
    if (d_lg10(large) > 2e3) {
/*<          SMALL = SQRT( SMALL ) >*/
        *small = sqrt(*small);
/*<          LARGE = SQRT( LARGE ) >*/
        *large = sqrt(*large);
/*<       END IF >*/
    }

/*<       RETURN >*/
    return 0;

/*     End of DLABAD */

/*<       END >*/
} /* dlabad_ */

#ifdef __cplusplus
        }
#endif