Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!brutus.cs.uiuc.edu!apple!sun-barr!newstop!sun!road!khb From: khb@road.Sun.COM (Keith Bierman - Advanced Languages - Floating Point Group ) Newsgroups: comp.sys.sgi Subject: Re: FORTRAN program optimisation Message-ID: <123703@sun.Eng.Sun.COM> Date: 26 Aug 89 02:19:52 GMT References: <89Aug25.093608edt.57688@ugw.utcs.utoronto.ca> Sender: news@sun.Eng.Sun.COM Reply-To: khb@sun.UUCP (Keith Bierman - Advanced Languages - Floating Point Group ) Organization: Sun Microsystems, Mountain View Lines: 45 In article <89Aug25.093608edt.57688@ugw.utcs.utoronto.ca> LEONARDZ@UOGUELPH.BITNET ("Len Zaifman UoGuelph 824-4120 xt 6566", 519) writes: > > I need help on two issues. > > 1 . I am trying to compile some fortran code with optimisation. At O2 , > several routines ( this program has several hundred ) hit .... stuff about table sizes It should be easy enough to try the experiment of compiling a few modules with and without the larger tables. I've never noticed a significant difference, but not working for SGI, I can't promise you that. > To that end I would also like someone from SGI to comment on the > advisability of using O3. I was told that at the moment this level of > optimisation is unsafe. Is that true , and what performance Mileage varies a lot for all higher level optimizers. I strongly suggest you profile your code, and turn the optimizer on high on just the top routines (probably 5 or 10). Optimizers can pessimize code, so pay attention to the profiles as you go. I expect that you have both prof and gprof. prof is less intrusive. For really reducing the intrusiveness (at the cost of lower information content) turn on profiling ONLY on the "link" line, viz. f77 -O your.f -c f77 your.o -p Asking how much benefit O gives over is typically silly ... most of the time doesn't matter ... just what goes on in 10% of your code. > > 2. On the user interface side , I see a need for easier command recall At the very least ksh should be available (if only via the ATT toolchest source program, or via bash from RMS). I haven't played around with the SGI machines enough to comment of the cut and paste (sunview, and openlook allow it). Keith H. Bierman |*My thoughts are my own. !! kbierman@sun.com It's Not My Fault | MTS --Only my work belongs to Sun* I Voted for Bill & | Advanced Languages/Floating Point Group Opus | "When the going gets Weird .. the Weird turn PRO"