[Beowulf] Re: vectors vs. loops

Joe Landman landman at scalableinformatics.com
Thu Apr 28 11:08:53 EDT 2005



Mikhail Kuzminsky wrote:
> In message from Joe Landman <landman at scalableinformatics.com> (Wed, 27 
> Apr 2005 15:51:49 -0400):
> 
>> Hi Art:
>>
>>   Any particular codes you have in mind?  I used to play around with 
>> lots of DFT (LDA) codes.  Back then, large systems were 256 x 256, 
>> with periodic BC's.
> 
> Most (practically all) DFT codes are not limited by eigenvalues
> problem. The limiting stage is computation of 2-electron integrals and
> fockian.

For the systems we were studying, the rate limiting step was the 
eigenvalue extraction.  We were using table lookups for the 2 and 3 
center integrals.  Then again, these were approximations built upon 
approximations ...


-- 
Joseph Landman, Ph.D
Founder and CEO
Scalable Informatics LLC,
email: landman at scalableinformatics.com
web  : http://www.scalableinformatics.com
phone: +1 734 786 8423
fax  : +1 734 786 8452
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