Re: [review][constrained_value] Review of Constrained ValueLibrary begins today

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.

Regards,
Ravi

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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