PSLABAD(3)    ScaLAPACK routine of NEC Numeric Library Collection   PSLABAD(3)



NAME
       PSLABAD  -  take  as input the values computed by PSLAMCH for underflow
       and overflow, and returns the square root of each of  these  values  if
       the log of LARGE is sufficiently large

SYNOPSIS
       SUBROUTINE PSLABAD( ICTXT, SMALL, LARGE )

           INTEGER         ICTXT

           REAL            LARGE, SMALL

PURPOSE
       PSLABAD takes as input the values computed by PSLAMCH 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 PSLAMCH.   This  subroutine  is  needed  because
       PSLAMCH  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) REAL
               On entry, the underflow threshold as computed by  PSLAMCH.   On
               exit, if LOG10(LARGE) is sufficiently large, the square root of
               SMALL, otherwise unchanged.

       LARGE   (local input/local output) REAL
               On entry, the overflow threshold as computed  by  PSLAMCH.   On
               exit, if LOG10(LARGE) is sufficiently large, the square root of
               LARGE, otherwise unchanged.



ScaLAPACK routine               31 October 2017                     PSLABAD(3)