bionic (3) pdlamch.3.gz

NAME

       PDLAMCH - determine double precision machine parameters

SYNOPSIS

       DOUBLE PRECISION FUNCTION PDLAMCH( ICTXT, CMACH )

           CHARACTER    CMACH

           INTEGER      ICTXT

PURPOSE

       PDLAMCH determines double precision machine parameters.

ARGUMENTS

       ICTXT   (global input) INTEGER
               The BLACS context handle in which the computation takes place.

       CMACH   (global input) CHARACTER*1
               Specifies the value to be returned by PDLAMCH:
               = 'E' or 'e',   PDLAMCH := eps
               = 'S' or 's ,   PDLAMCH := sfmin
               = 'B' or 'b',   PDLAMCH := base
               = 'P' or 'p',   PDLAMCH := eps*base
               = 'N' or 'n',   PDLAMCH := t
               = 'R' or 'r',   PDLAMCH := rnd
               = 'M' or 'm',   PDLAMCH := emin
               = 'U' or 'u',   PDLAMCH := rmin
               = 'L' or 'l',   PDLAMCH := emax
               = 'O' or 'o',   PDLAMCH := rmax

               where

       eps   = relative machine precision
             sfmin  =  safe  minimum,  such  that  1/sfmin does not overflow base  = base of the machine prec  =
             eps*base t     = number of (base) digits in the mantissa  rnd    =  1.0  when  rounding  occurs  in
             addition,  0.0  otherwise  emin   =  minimum  exponent before (gradual) underflow rmin  = underflow
             threshold - base**(emin-1) emax  = largest exponent before overflow rmax  = overflow  threshold   -
             (base**emax)*(1-eps)