Subject: SUMMARY: MB (or MW) in Gaussian 94

From: "M. Nicklaus" <[email-masked]>
Date: Wed, 1 Apr 1998 10:25:02 -0500 (EST)

Hi,

I asked the following

QUESTION
========
> How does G94 count one MB (or MW) in the %Mem command?
> Is it 1 x (or 8 x) 1,000,000;    
> or 1 x (or 8 x) 2^20 = 1 x (or 8 x) 1,048,576 ?
> 
> Hence, do the commands
> %Mem=8000000
> %Mem=8MW
> %Mem=64MB
> all mean exactly 64,000,000 or 67,108,864 bytes?
> 
> I tend toward the first interpretation, but since the
> manual does not seem to spell this problem out explicitly,
> I thought I'd ask...

If we go with Doug Fox's answer, then the Gaussian 94 User's
Reference is wrong.  On p. 10, it states:
   "For example, the following command sets memory use to 64 MB:
    %Mem=8000000
    [... T]he following command also sets the amount of 
    dynamic memory to 64 MB:
    %Mem=64M"

Can this be confirmed?

Here are the 

RESPONSES
=========

Brian Salter-Duke <[email-masked]>

8000000 means 8MW or 64,000,000 bytes. I tend to avoid using anything
in this command other than in words. MW may not work correctly. It
certainly does not in the %rwf line.

---------

Rick Venable <[email-masked]>

Your real question is the meaning of MEGA in these contexts; certainly
64MB has to be 64*1024*1024 by definition, but it's less clear for a
megaword, although one would hope for consistency.  My guess is that 8MW
== 64MB, but not 8000000 words.  You should be able to test this
empirically, I would think. 

---------

[email-masked] (Doug Fox)

    MB and MW are powers of 2 not decimal numbers so  8000000
is not identical with 8MW or 64MB.  The latter two are identical
and have the value of 6710864.  
   [I guess you meant 67108864. M.N.] 
------------------------------------------------------------------------

Marc

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 Marc C. Nicklaus                        National Institutes of Health
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    Laboratory of Medicinal Chemistry, National Cancer Institute,  &
 Center for Molecular Modeling, Div. of Computer Research and Technology
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