From jkl-: at :-ccl.net Tue Jun 25 13:03:02 1991
Date: Tue, 25 Jun 91 13:06:26 -0400
From: jkl;at;ccl.net
To: chemistry "-at-" ccl.net
Subject: Re: Machine epsilon
Status: R

Here is even a simpler way for macheps for Dr. Elbert
---------- Begin Forwarded Message ----------
> From elbert -x- at -x- tc1.chem.iastate.edu Tue Jun 25 12:38:19 1991
> Date: Tue, 25 Jun 91 11:40:12 CDT
> From: elbert #at# tc1.chem.iastate.edu (Stephen T. Elbert)
> To: jkl- at -ccl.net
> Subject: Machine epsilon

A much simpler, faster way of computing eps is

        a = 4.d0/3.d0
  10    b = a - 1.0d0
        c = b + b + b
        eps = abs(c - 1.0d0)
        if (eps .eq. 0.0d0) go to 10

This code has been used by EISPACK for years.  The branch is to keep the
compiler from using possibly incorrect register values.

Stephen Elbert               Iowa State University    515-294-1307 voice mail
                             Ames Laboratory - USDOE  515-294-3226 FAX
elbert(+ at +)IaState.edU           315a Wilhelm Hall
elbert /at\alisuvax.bitnet       Ames, IA 50011

----------- End Forwarded Message -----------