Subject: Summary: g98/linux: a disk usage problem

From: <[email-masked]>
Date: Wed, 2 Jan 2002 07:32:03 -0500 (GST)

Dear CCLers,

the responses to my "disk usage problem" question could be summarized as:
The MaxDisk parameter is a true maximum only for MP2 energy and gradient 
calculations, but not for MP2 NMR properties. For correlated energy 
calculations in general, the experience shows that the input "MaxDisk" 
parameter has to be significantly lower than the true disk space available 
(sometimes as little as 1/2 of the available disk) to get the job through. 
A summary of the responses is given below; many thanks to Gaussian 
Customer Service, Mark Sayes, Laurence Cuffe, Juan Pablo Senosiain,  Wang 
Dongqi, and Mark Russel for their help.

Marketa

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Date: Thu, 20 Dec 2001 09:14:20 -0500 (EST)
From: Cust. Service Doug <[email-masked]>
Reply-To: [email-masked]
To: [email-masked]
Subject: Re: CCL:g98/linux: a disk usage problem

  Marketa,

   The MaxDisk input parameter is a true maximum only for MP2 energy
and gradient calculations where it is almost always possible to choose
and algorithm which can reduce the disk below MaxDisk.  The MP2 Freq
MP2 NMR and post MP2 calculations have some choices but must store the
MO integrals and then do batches on the remaining disk so there is a
disk threshold below which you cannot go and do the calculation.

  Based on what you show here you have hit that limit.  All the
input limits seem to have been recognized and the program is
simply in need of more disk.

  What platform are you using and how big is the system?  On some
systems it might be possible to augment your disk and go forward.
Also which revision of G98 are you using?
------

Date: Thu, 20 Dec 2001 09:08:56 +0100
From: Mark Saeys <[email-masked]>
To: "[email-masked]'" 
<[email-masked]>
Subject: RE: g98/linux: a disk usage problem

I have the same problem with large MP2 calculations and with CCSD(T)
calculations as well. I usually set MaxDisk fairly low -much lower than 
the
amount of rwf-files I allocated (sometimes only half of that). G98 looks 
at
the MaxDisk to choose the algorithm it uses, but does violate MaxDisk. If
you put MaxDisk too low, the calculation will abort quite quickly.

Unfortunately, that is not a very elegant way-if you find a better
solution, please let me know.

Best Regards,
Mark

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Date: Thu, 20 Dec 2001 14:34:30 -0800
From: Juan Pablo Senosiain <[email-masked]>
To: [email-masked]
Subject: Re: CCL:g98/linux: a disk usage problem

Hi Marketa,

I've had similar problems running large QCISD(T) calculations in the
past.   These are some of the things that I've learned:

- the  MaxDisk keyword doesn't always work
- for some reason some file systems don't allow files 2GB or larger, but
you shouldn't have any problems if you specified filelengths less than
this, such as 2040MB.
- in trying to specify many RWF files, I've been limited to the number of
files I can write in an 80 character line. I think this is not the case 
for
the newer Gaussian revisions (e.g. Rev A9) which allow lines to be up to
500 characters in length
- using  SCF(direct) eliminates the necessity of storing the AO's, saving
some space on disk.
- transformation=semidirect reduces the disk requirements.

good luck.

  Juan Pablo

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Date: Wed, 19 Dec 2001 18:09:16 +0000
From: Laurence Cuffe <[email-masked]>
To: [email-masked]
Subject: Re: CCL:g98/linux: a disk usage problem

In g94 the keyword would have been MP2=(veryStingy), however
even when this worked an MP2 job would look for more diskspace
than the maxdisk limitation if it needed it. so the behaviour your
seeing is probably not a compilation problem.  Do you have a
%MEM directive in your input file or your Default.route file? try
setting this to the largest value you can as gaussian often
assumes if its not told otherwise that there is very little physical
memory available.  that's about all I can think off except trying
MP2=FullDirect but unless you have lots of RAM I wouldn't be
optimistic about this working.
Hope this helps
All the best
Laurence Cuffe

---------

Date: Thu, 20 Dec 2001 20:16:33 +0800
From: wangd <[email-masked]>
To: [email-masked]
Subject: RE: CCL:g98/linux: a disk usage problem

hi, Marketa,

  First, please confirm that you have enough disk space. If that is true, 
try
%RWF=a,1800MB,b,1800MB,c,1800MB,d,1800MB,e,1800MB,f,1800MB,g,-1   It 
should
work.

Good luck!
Wang Dongqi

Wang Dongqi
Department of Chemistry,
University of Hong Kong,
Pokfulam Road,
Hong Kong
Tel:(852)28598947

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Date: Wed, 19 Dec 2001 16:32:46 +0000 (GMT)
From: Mark Russell <[email-masked]>
To: [email-masked]
Subject: Re: CCL:g98/linux: a disk usage problem

>  MaxDsk=  1610612736 LAFull=   434653128 LimDsk=  1610612736

I think that MaxDsk is displaying its requirements in words not bytes, so
you have to multiply the number by 8 to get the space in bytes - around 12
gigabytes I think!  ;-)

> my disk capacity). Is there a stronger way of telling the code how much 
disk
> can be used, or can this be a compilation-related problem? Many thanks
> for any hint.

I think that Gaussian will use whatever amount of space it needs, but will
try to keep within the limits that you set.  However, if it needs to use
more than you tell it, then it will use whatever it wants.  If you find
out from someone on the list about a stronger way of limiting the usage,
then I'd be interested in the information as well.

Cheers,

Mark Russell