DLAMCH (3lapack)

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)