man dlamch (Fonctions bibliothèques) - determine double precision machine parameters

NAME

DLAMCH - determine double precision machine parameters

SYNOPSIS

DOUBLE PRECISION
FUNCTION DLAMCH( CMACH )
CHARACTER CMACH

PURPOSE

DLAMCH determines double precision machine parameters.

ARGUMENTS

CMACH (input) CHARACTER*1
Specifies the value to be returned by DLAMCH:

= 'E' or 'e', DLAMCH := eps

= 'S' or 's , DLAMCH := sfmin

= 'B' or 'b', DLAMCH := base

= 'P' or 'p', DLAMCH := eps*base

= 'N' or 'n', DLAMCH := t

= 'R' or 'r', DLAMCH := rnd

= 'M' or 'm', DLAMCH := emin

= 'U' or 'u', DLAMCH := rmin

= 'L' or 'l', DLAMCH := emax

= 'O' or 'o', DLAMCH := 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)