Subject: Bug affecting MacroModel on SGI O2, Origin, Octane Platforms

From: "Peter Shenkin" <[email-masked]>
Date: Fri, 23 May 1997 12:12:59 -0400

I've sent this to the MacroModel user's mailing list
([email-masked]), but it occurs to me that there are probably
MacroModel users who read CCL that don't read mmodlist, and I thought
this was important enough to post.

Also, other program may be affected as well, so perhaps it's of
more general interest after all.

It turns out that there's a system bug on several SGI platforms that
prevents BatchMin from operating correctly.  The platforms I know of
that are affected are: the O2 and Origin machines;  the Octane
is probably affected as well.

On the O2 the program simply doesn't run, but on the Origin it runs
but produces incorrect results -- so watch out!

The bug can be fixed in all cases by installing Patch 1775 from SGI.

There are also workarounds.

The simplest workaround is to run a -mips2 version of BatchMin
rather than a -mips4 version;  from the GUI, this requires going
into the Host selection and selecting a -mips2 version.

On the O2, the following alternative also works, if done as root:

# cd /usr/lib32
# ln -s mips3/libfastm.so .

This creates the file /usr/lib32/libfastm.so as a symbolic link to 
the version in /usr/lib32/mips3.

The nature of the bug on the O2 is two-fold.  First, libfastm.so
is missing from /usr/lib32, and as a result the mips4 version of
BatchMin cannot start up.  Second, /usr/lib32/mips4/libfastm.so
is defective, and should not be used.  Patch 1775 supplies a
fixed version, and the workaround described above uses the mips3
version instead, which works but is not quite as highly optimized
as a good mips4 version would be.

On Origin systems, /usr/lib32/libfastm.so is found, so the program
starts up, but the mips4 library is still defective, so the program
gives wrong answers.  The only workaround which I've verified is
to use the mips2 version; in addition, I've verified personally
that Patch 1775 fixes the problem.

On the O2, earlier versions (pre-6.0) of BatchMin encounter
no problems, since for earlier versions only the mips2 version can
run on this platform in any case, and this version works well;  but
on the Origin and (I think) the Octane, which can run 64-bit codes,
I would expect that older versions of BatchMin would suffer the
same problems as 6.0.

(N.B.  For Mmod 6.0, we compile our -mips4 code versions using the 
-n32 ABI, which allows all -mips4 platforms to run the codes;  
previously, the -mips4 code used the -n64 ABI, which limited
execution to IRIX64 platforms, such as the PowerChallenge and
Origin.)

	-P.

-- 
**** "Deep Blue can't triumph in the game of life" (NY Times, 5/13/97) ****
* Peter S. Shenkin; Chemistry, Columbia U.; 3000 Broadway, Mail Code 3153 *
** NY, NY  10027;  [email-masked];  (212)854-5143;  FAX: 678-9039 ***
*MacroModel WWW page: http://www.columbia.edu/cu/chemistry/mmod/mmod.html *