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dlamch

 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 over-
            flow 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)