bionic (3) pdlabad.3.gz

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.