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Subject: Re: [boost] [review][constrained_value] Review of Constrained ValueLibrary begins today
From: Ravi (lists_ravi_at_[hidden])
Date: 2008-12-09 12:11:00

On Monday 08 December 2008 22:26:40 Gordon Woodhull wrote:
> Yes, floating point predicates should be a separate library, and the  
> floating point FUD should be removed from the documentation as well.

The points made about floating point are not FUD. They are facts of life for
people working with high precision floating point computations; in fact, a lot
of such computations go through severe contortions to avoid/mitigate said
problems without compromising performance too much. Just as an example, try
summing an array of 1000 normally distributed doubles naively and with atlas
(or any other optimized BLAS); you will see that the actual result (not the
computation time) differs because the optimized BLAS takes into account the
vagaries of floating point computation.

Given that there are so many facets of floating point computations that are
unclear even to those on this list, providing a library with a lot of built-in
assumptions about epsilons and the like would be a support headache for a long
time. It is very easy to be misled about the effects of floating point
computations on commodity hardware.


PS: This discussion reminds me very much about the floating point
serialization discussion a few weeks back. Working with floating points
requires deep domain expertise in the general case; the best solution, in my
humble opinion, is to simply wrap the work of the HPC community rather than
reinvent the (very complicated) wheel.

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