forked from lijiext/lammps
106 lines
3.0 KiB
Fortran
106 lines
3.0 KiB
Fortran
*> \brief \b DLABAD
|
|
*
|
|
* =========== DOCUMENTATION ===========
|
|
*
|
|
* Online html documentation available at
|
|
* http://www.netlib.org/lapack/explore-html/
|
|
*
|
|
*> \htmlonly
|
|
*> Download DLABAD + dependencies
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlabad.f">
|
|
*> [TGZ]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlabad.f">
|
|
*> [ZIP]</a>
|
|
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlabad.f">
|
|
*> [TXT]</a>
|
|
*> \endhtmlonly
|
|
*
|
|
* Definition:
|
|
* ===========
|
|
*
|
|
* SUBROUTINE DLABAD( SMALL, LARGE )
|
|
*
|
|
* .. Scalar Arguments ..
|
|
* DOUBLE PRECISION 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 ..
|
|
DOUBLE PRECISION 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
|