Path: utzoo!attcan!uunet!husc6!uwvax!vanvleck!uwmcsd1!csd4.milw.wisc.edu!zdenko From: zdenko@csd4.milw.wisc.edu (Zdenko Tomasic) Newsgroups: comp.unix.aux Subject: Re: file size Message-ID: <6034@uwmcsd1.UUCP> Date: 18 Jun 88 14:56:34 GMT References: <6000@uwmcsd1.UUCP> <1190@unisoft.UUCP> Sender: daemon@uwmcsd1.UUCP Reply-To: zdenko@csd4.milw.wisc.edu (Zdenko Tomasic) Organization: University of Wisconsin-Milwaukee Lines: 51 In article <1190@unisoft.UUCP> john@unisoft.UUCP (John Sovereign) writes: > >A/UX inherits support for file size limits from System V, >which provides a ulimit(2) system call that allows a process >to query and set its file size limit (among other things). >The ulimit(2) file size is defined in 512-byte blocks and >may only be increased if you're root. > >The default limit in A/UX is equivalent to 8 GB, which exceeds >the size which you may actually create since the file offset is >an unsigned long (32-bits). > Thanks for the info! >Let me know if you ever create a 2 GB file. :-> ^^^^ > Let's see: In quantum chemistry calculations, in order to calculate electronic energy (including electron correlation) of a substance, one needs roughly N**4/8 integrals. N is a size of a basis functions used in integral calculation. If one sticks to not-so-big 4-31G basis set which includes 2 functions for hydrogen (H) and 9 for carbon (C), oxygen (O) and nitrogen (N) each, the ordinary CHOLESTEROL molecule (C27H46O) will require N of 344 (=27*9+46*2+9) basis functions. In that case there are 1 750 426 112 integrals which in double precision (with 8 bytes per integral) means a file of 14 003 408 896 bytes, i.e. more than 14 GB. ^^^^^ Of course, one would not try that on Mac, but maybe (or maybe not even there!) Cray or ETA-10 . You see, such big files are not all that unusual, not to mention real big bio-molecules (hundreds, thousands of atoms). They are naturally out of reach for serious calculations with present resources. >John Sovereign >UniSoft Corporation >uunet!unisoft!john >#include Zdenko Tomasic UWM, Chem. Dept. Milwaukee,WI,53201 __________________________________________________________ UUCP: ihnp4!uwmcsd1!uwmcsd4!zdenko ARPA: zdenko@csd4.milw.wisc.edu __________________________________________________________