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)

  —  LAPACK version 2.0  —  08 October 1994