Floating Point Expectations

[Doug Gwyn]

In article <1603:May2720:32:5190 at stealth.acf.nyu.edu> brnstnd at stealth.acf.nyu.edu (Dan Bernstein) writes:
-In article <13000 at smoke.BRL.MIL> gwyn at smoke.BRL.MIL (Doug Gwyn) writes:
-> Rather than attempting to model exact behavior of floating-point systems,
-> I recommend devising algorithms that are robust in the face of
-> considerable cruft from the floating-point unit.
-This doesn't remove from FPU makers the responsibility to make chips
-satisfying reasonably simple rules. You really can get a lot better
-performance out of numerical algorithms when, e.g., you're working under
-Knuth's model of floating-point computation. ANSI floating-point is an
-excellent start, and it's worth the effort for strict compliance.

Unfortunately, in the real world the programmer cannot specify the
properties of the floating-point hardware.  There are numerous kinds
of FP architectures and implementations, each with its own set of
inaccuracies.  I stand by what I said -- instead of relying on the
FP model, make the algorithms robust.