C DLABAD SOURCE BP208322 18/07/10 21:15:04 9872
*> \brief \b DLABAD
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
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*
* Definition:
* ===========
*
* SUBROUTINE DLABAD( SMALL, LARGE )
*
* .. Scalar Arguments ..
* REAL*8 LARGE, SMALL
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> 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.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in,out] SMALL
*> \verbatim
*> SMALL is 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.
*> \endverbatim
*>
*> \param[in,out] LARGE
*> \verbatim
*> LARGE is 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.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date December 2016
*
*> \ingroup OTHERauxiliary
*
* =====================================================================
SUBROUTINE DLABAD( SMALL, LARGE )
*
* -- LAPACK auxiliary routine (version 3.7.0) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* December 2016
*
* .. Scalar Arguments ..
REAL*8 LARGE, SMALL
* ..
*
* =====================================================================
*
** .. 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
SMALL = SQRT( SMALL )
LARGE = SQRT( LARGE )
END IF
*
RETURN
*
* End of DLABAD
*
END