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Re: g77; numerical accuracy; 80 bit spills


The `Floating point precision' node of the manual was written by a
physicist/programmer, though perhaps it won't be left in long.  Do you
actually have a problem following its advice?  I've heard of only one
real case where it apparently didn't solve the x86 extended precision
problem (because of the remaining extended exponent range for reasons
I don't recall).

I also supplied the references in `Floating-point Errors' (after
reading them and before they appeared elsewhere and became fashionable
to quote).  See particularly the new appendix to the Goldberg paper.

[Yes, in _some_ cases a 50% speed penalty might be significant to me
(my users).  But note that sometimes you can pay an arbitrary price
for IEEE compliance.  I have seen the order of magnitude sort of
slowdown mentioned in the Sun numerical computation guide (should be
at http://docs.sun.com) in real life.  Life's hard and these things
aren't black and white in my book after embarrassingly long experience
which often seems to be wasted.]

BTW, anyone who thinks that there are unique issues with g77 in such
regards, and that writers of potentially-ported code don't have to be
careful, hasn't had to support as many systems as I have (often
without actual access to them or proper docs).  That was my main
motivation for trying to contribute to g77, regardless of GNU
sympathies.


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