Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!elroy.jpl.nasa.gov!ames!skipper!altair!maine From: maine@altair.dfrf.nasa.gov (Richard Maine) Newsgroups: comp.lang.fortran Subject: Re: FORTRAN and (un)SAVEd vars Message-ID: Date: 6 Mar 91 05:27:10 GMT References: <8@interet.UUCP> <1991Feb28.004447.3728@nas.nasa.gov> <4849@goanna.cs.rmit.oz.au> <1991Feb28.164256.23516@nas.nasa.gov> <1991Mar5.194219@fman.enet.dec.com> Sender: news@skipper.dfrf.nasa.gov Organization: NASA Dryden, Edwards, Cal. Lines: 25 In-reply-to: khb@chiba.Eng.Sun.COM's message of 6 Mar 91 02:07:57 GMT On 6 Mar 91 02:07:57 GMT, khb@chiba.Eng.Sun.COM (Keith Bierman fpgroup) said: Keith> In article <1991Mar5.194219@fman.enet.dec.com> peterson@fman.enet.dec.com (Bob Peterson) writes: Bob> it be a safe bet that SAVEd variables operate as fast or faster than Keith> No. SAVEd variables must be written to memory. UnSAVEd variables may Keith> turn out to be just register references. Also, if there are multiple subroutines with large SAVEd arrays, this can increase the program's memory usage enough to slow things down (or even keep them from running at all). If these multiple subroutines are never simultaneously "active" in the call chain, (for instance if they are alternative algorithms) then an unSAVED equivalent can be smaller and faster. This kind of thing does happen in real programs. Of course, it is only an issue for arrays; scalar variables are very unlikely to take enough space to have noticable effect. -- -- Richard Maine maine@altair.dfrf.nasa.gov