From chemistry-request@ccl.net Mon Oct 14 21:09:39 1991 Date: Tue, 15 Oct 91 08:56:26 SST From: Heng Kek Subject: Estimation of INT and RWF file sizes for G86 (Summary) To: Computational Chem Grp at Ohio Supercom Ctr Status: R Hi all, A while ago, I posted the following question. Now here's the summary of all the responses I got: >* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 41 > >Question: Is there a way to calculate beforehand, the size of the > INTEGRAL and RWF files, given the input to the G86 program? > >* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 40 >From: >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@uno" >University of New Orleans >Dept of Chemistry >From: > >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. > >* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * = >From: djh@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@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?" > >* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * = >From: > >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 > >* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * = >From: m10!frisch@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. >------- Acknowledge-To: