NAME
PDLABAD - take as input the values computed by PDLAMCH for underflow
and overflow, and returns the square root of each of these values if
the log of LARGE is sufficiently large
SYNOPSIS
SUBROUTINE PDLABAD( ICTXT, SMALL, LARGE )
INTEGER ICTXT
DOUBLE PRECISION LARGE, SMALL
PURPOSE
PDLABAD takes as input the values computed by PDLAMCH 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 PDLAMCH. This subroutine is needed because
PDLAMCH does not compensate for poor arithmetic in the upper half of
the exponent range, as is found on a Cray.
In addition, this routine performs a global minimization and maximi-
zation on these values, to support heterogeneous computing networks.
ARGUMENTS
ICTXT (global input) INTEGER
The BLACS context handle in which the computation takes place.
SMALL (local input/local output) DOUBLE PRECISION
On entry, the underflow threshold as computed by PDLAMCH. On
exit, if LOG10(LARGE) is sufficiently large, the square root of
SMALL, otherwise unchanged.
LARGE (local input/local output) DOUBLE PRECISION
On entry, the overflow threshold as computed by PDLAMCH. On
exit, if LOG10(LARGE) is sufficiently large, the square root of
LARGE, otherwise unchanged.