Estimation of INT and RWF file sizes for G86 (Summary)
Hi all,
A while ago, I posted the following question. Now here's the summary
of all the responses I got:
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>
>Question: Is there a way to calculate beforehand, the size of the
> INTEGRAL and RWF files, given the input to the G86 program?
>
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>From: <SEMINARI "at@at" CPWPSCA>
>The maximum size of the files can be estimated exactly but is a little
>dificult and experience plays an important role.
>The easier to determine is integral file because the maximum
>number of integrals is roughly (N**4)/8 where N is the number of basis
>functions. Each integral will need from 10 to 16 bytes depending on the
hardwar
>used. I know nothing about the SX. The program will eliminate small
integrals
>so the total number of integrals reduces from 5 to 30%, Therefore
>experience in your systems will tell you a good estimate but knowing
>the maximum is a good start. Later versions of gaussian (89,90,91) have
>a DIRECT option in which you do not need to storage integrals and
>is even faster when the total number of basis functions is bigger than 100.
>Normally the RWF do not require lot of space exept in postHF
>calculations where the above number have to multiplied by the number
>of atoms in same cases or the number of occupaid orbitals etc the
>deatails must be in the manual. Again, for these calculations
>this is not true in latest versions of Gaussian. I used G90
>which is more eficient managing disk space. You should get G90 or
>at least G88. G86 was not a good version (has many bugs)
>and not many people use it right now. There are many details involved
>I guess if you mail me the input file, could be of more help.
>Best regards
>Dr. Jorge M. Seminario
>bitnet%"jsmcm "at@at" uno"
>University of New Orleans
>Dept of Chemistry
>From: <SEMINARI "at@at" CPWPSCA>
>
>The problem with the RWF file is that its content have changed with
>different versions of Gaussian, you probably can see the exact content
>in the manual. I do not have one right now. A 94 basis functions MP2
>calculation would require the following disk space:
>---------------------------------from output file---------------------------
>0Normal termination of Gaussian 90.
> STATUS OF FILES
> RWF: /tmp/users/4/seminari/sco1/97269/g90-a97282.rwf 453120 words deleted
> INT: /tmp/users/4/seminari/sco1/97269/g90-a97282.int 19326464 words deleted
> D2E: /tmp/users/4/seminari/sco1/97269/g90-a97282.d2e 0 words deleted
> CHK: sco1mp2.chk 130560 words saved
> SCR: /tmp/users/4/seminari/sco1/97269/g90-a97282.scr 24668160 words deleted
> -----------------------------------------------------------------------end
>This can help you a little to have an idea (remember 1word=8bytes)
>In MP2 calculations RWF (G86) it probably contains the transformed integrals
>and some other stuff for the frequency so the g86 would
>contains the RWF and the SCR files of G90 plus an small additional for the
>numerical second derivatives. But a word of advice here,
>MP2 FREQ in Gaussian are done numerically as opposed to analytically
>which for your system could take many times less
>CPU time! (12 atoms means 36 coordinates so 72+1 energy calculations will
>be required numerically.) The program that can do that analytically is
>called CADPAC (Cambridge Analytic Derivative PACkage) I never do MP2 FREQ
>using Gaussian programs.
>
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>From: djh "at@at" ccl.net
>
>>The problem: G86 on the SX uses a tremendous amount of scratch filespace
>
>For SCF-only jobs (that is, no MP, CI, etc.) find out how many basis
functions
>there are. The easiest way to do this is start up the job for a minute or
so
>and look through the output. If N is the number of basis functions,
estimate
>N^4/4 words of storage needed for the integral file. I assume the SX is a
>64 bit machine, so if there are 50 basis functions you'd need 12.5MB.
>
>If there is symmetry in the molecule you won't need as much space. If the
>user is doing a correlated calculation, you may need several times this
space.
>
>Often, many similar jobs are run, or a series of runs with larger basis sets
is
>made, so an aware user can make a good estimate of file space needed after
the
>first successful run. Unfortunately, experience is the only good teacher in
>this problem!
>
>>Another question is: Is this sort of filesize for the integrals and
>>readwrite file typical??
>
>We routinely run jobs requiring 8GBytes total disk space. Quantum chemistry
>does not scale well! You might want to look into getting G90 though, as it
>has the so-called "direct SCF", which uses only minimal disk space
at some
>increase in CPU time.
>--
>David J. Heisterberg (djh "at@at" ccl.net) "Dost thou use to write thy
name?
>The Ohio Supercomputer Center or hast thou a mark to thyself,
>Columbus, Ohio like an honest plain-dealing man?"
>
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>From: <NEELY "at@at" AUDUCVAX>
>
>I'm a bit surprised that the rwf file takes more space than the
>integral file: whenever I've run G86 on a Cray, the reverse
>was true. A pretty decent estimate for the integral file is
>10*N*N*N*N/4 bytes, where N is the number of basis functions.
>This number can be obtained from the molecular formula, and
>knowledge of the basis set. Tim Clark, in his "Handbook of
>Computational Chemistry" (Wiley, I think) has a nice chart of
>the number of basis functions per atom for the common basis sets.
>I hope this helps you.
>Irene Newhouse
>
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>From: m10!frisch "at@at" uunet.UU.NET (Michael Frisch)
>
>It is common for ab initio calculations to use large amounts of disk space.
>The current version of Gaussian can trade CPU time for disk space for the
>most common types of calculation (Hartree-Fock and MP2), and is much, much
>faster, but these capabilities were not present in Gaussian 86.
>
>The integral file size depends on the number of basis functions. It will be
>roughly 1.5N^4 bytes or 2N^4 bytes long, depending on how the integral
>labels are packed (whether they fill 32 or 64 bits). For open-shell
>Hartree-Fock calculations, the size will be 2.5N^4 or 3N^4.
>
>The read-write file size depends on N^2 for Hartree-Fock calculations, and
>on N^4 in a complicated way for post-SCF calculations. The easiest way to
>estimate the size is to run a smaller job an scale the size by the ratio
>of OV^3 for the jobs (O=number of electrons, V=N-O=number of virtuals).
>
>The limitation of not being able to extend these files is specific to the
>NEC implementation of Gaussian and is not present on other versions.
Contact
>your NEC representative for an explanation.
>
>All this is for Gaussian 86, of course. For SCF and MP2 calculations in
>Gaussian 90 the integral file isn't needed. For MP2, whatever disk is made
>available for the read-write file is used, with quantities being recomputed
>instead of trying to use more disk than there is.
>
>Michael Frisch
>Gaussian, Inc.
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Acknowledge-To: <CCECHK "at@at" NUSVM>