What is acceptable for -ffast-math? (Was: associative law in combine)

[Per Abrahamsen]

dewar@gnat.com writes:

> Well it sure would be nice to here from some of these mythical numerical
> programmers (I don't care if they are writing games or nuclear reactor codes)
> who would be happier, so far we haven't heard this! 

I'm writing agricultural simulations[1], and I'd be happy to get
transformations enabled with -ffast-math that would be safe with real
numbers, but not with floating point numbers.

And I'm one of those incompetant programmers that are forced to write
a * b + a * c rather than a * (b + c), when the former is easier to
understand, i.e. closer to the original problem.  Otherwise my small
brain can simply not grasp what the code was meant to signify, when I
reread it later.

So we aren't quite mythical.  Maybe we really ought to be shoot and
replaced by Real Programmers(TM), but there seem to be a shortage of
those, so that is not likely to happen soon.

Footnotes: 
[1]  See <URL: http://www.dina.kvl.dk/~daisy/ >.