p?lamch

Syntax

Include Files

The C interfaces are specified in the mkl_scalapack.h include file.

Description

The p?lamch routine determines single precision machine parameters.

Input Parameters

ictxt

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

cmach

(global) CHARACTER*1.

Specifies the value to be returned by p?lamch:

= 'E' or 'e', p?lamch := eps

= 'S' or 's' , p?lamch := sfmin

= 'B' or 'b', p?lamch := base

= 'P' or 'p', p?lamch := eps*base

= 'N' or 'n', p?lamch := t

= 'R' or 'r', p?lamch := rnd

= 'M' or 'm', p?lamch := emin

= 'U' or 'u', p?lamch := rmin

= 'L' or 'l', p?lamch := emax

= 'O' or 'o', p?lamch := 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)

Output Parameters

val

Value returned by the routine.