Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!batcomputer!munnari.oz.au!metro!news
From: moss_r@summer.chem.su.oz.au (Richard Moss)
Newsgroups: comp.sys.apollo
Subject: ftn 10.7 and f77 - problem
Message-ID: <1991Apr9.043538.4195@metro.ucc.su.OZ.AU>
Date: 9 Apr 91 04:35:38 GMT
Sender: news@metro.ucc.su.OZ.AU
Organization: Dept. of Theoretical Chem, Uni. Sydney
Lines: 28
Nntp-Posting-Host: 129.78.76.12


I know the latest craze is finding bugs with ftn 10.8, but I've found a problem
using
ftn 10.7, or at least the f77 front end to it...


For the last few weeks I have been writing a fairly long monte carlo particle 
simulation code.  After getting rid of all the bugs, I tried compiling it with 
f77 and ftn option -opt 4.

It no longer worked !

With no optimization and -dba everything was fine.  Above -opt 2 the program
just
didn't work properly.

I was using "f77 -W0,-opt 4".  If I used "f77 -W0,-opt 4,-xrs" instead
everything was 
fine and dandy again. 

Using /usr/apollo/lib/ftn by hand ( without -xrs ) also worked fine.

What does f77 do that stuffs up the higher optimisation levels ?  

thanks
            Richard Moss
            dep't theoretical chemistry, Sydney University
            moss_r@summer.chem.su.oz.au