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From: system@alchemy.chem.utoronto.ca (System Admin (Mike Peterson))
Newsgroups: comp.sys.apollo
Subject: Re: Floating point
Summary: Use an environment variable
Keywords: floating
Message-ID: <1990Sep21.172129.13644@alchemy.chem.utoronto.ca>
Date: 21 Sep 90 17:21:29 GMT
References: <9009181421.AA22513@richter.mit.edu> <4ce36164.12c9a@digital.sps.mot.com> <4ce8cf0c.20b6d@apollo.HP.COM>
Organization: University of Toronto Chemistry Department
Lines: 35

None of this nonsense would be necessary if the following suggestion,
which I made to Apollo 2 years ago, had been acted on:

1) if the user specifies a "cpu" option, use it.

2) check an environment variable, called FLOAT at our site, to see what
   the default floating point compilation option should be.

3) use "cpu any" for m68k nodes.

Note the 1) and 3) is exactly what happens now, to the great detriment
of anyone who has either a M6888[12] or fpa (or other old fpu addon),
but doesn't know how to make the compiler use it properly. It is
especially painful from UNIX environments, since most people don't
invoke 'f77' directly, but rather use 'make', and the syntax to set the
Aegis options is more involved from 'f77' than from 'ftn'.

Having an environment variable solves all the problems, and it should be
set by the boot script AUTOMATICALLY to the correct option - no
intervention by the SysAdmin to set it is needed, since 'config' knows
what your system has.
At our site, FLOAT is set in the .cshrc/.profile file depending on the
node name, and EVERY [Mm]akefile HAS TO BE MODIFIED. This is RIDICULOUS,
but the only way to get maximum performance out of our DN2500,
DN4500/fpa and DN10000 systems (we recompile all floating point code for
each environment).

Since this approach outlined above is already in use by a competitor,
who introduced it to help users cope with ~5 different cpu/fpu
combinations (about what HP/Apollo has got now), I suspect it will never
happen on HP/Apollo systems, but it should.
-- 
Mike Peterson, System Administrator, U/Toronto Department of Chemistry
E-mail: system@alchemy.chem.utoronto.ca
Tel: (416) 978-7094                  Fax: (416) 978-8775