SUBROUTINE DLABAD( SMALL, LARGE )
*
* -- LAPACK auxiliary routine (version 3.2) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2006
*
* .. 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
SMALL = SQRT( SMALL )
LARGE = SQRT( LARGE )
END IF
*
RETURN
*
* End of DLABAD
*
END