p?lamch

Determines machine parameters for floating-point arithmetic.

Syntax

float pslamch (MKL_INT *ictxt , char *cmach );

double pdlamch (MKL_INT *ictxt , char *cmach );

Include Files

  • mkl_scalapack.h

Description

The p?lamchfunction determines single precision machine parameters.

Input Parameters

ictxt

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

cmach

(global)

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 - (baseemax)*(1-eps)

Output Parameters

val

Value returned by the function.

See Also

For more complete information about compiler optimizations, see our Optimization Notice.
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