fastmath library?

William Park parkw at better.net
Thu Nov 16 23:42:29 CET 2000


On Thu, Nov 16, 2000 at 03:18:33PM -0600, William Annis wrote:
> "Pete Shinners" <pete at visionart.com> writes:
> 
> > one that uses high-speed lookup tables and estimates for
> > low quality results? i'd mainly like one that can handle
> > things like square-root, cosine, etc, etc
> 
>         This lookup-don't-compute behavior is sometimes called
> memoizing.  
> 
> > i figure there's got to be something like this already
> > available for python?
> 
>         Well I've written the little memoizing class below.  I'm not
> sure the overhead will help you in the case of sine and cosines, but
> certainly will for more complex functions:

<cut>...</cut>

>         Basically, it keeps a dictionary of arguments.  When it has
> seen the arguments before, it just looks up the data.  When they're
> new, it does the computation.  So, this is only helpful when you're
> calling the memoized function a lot.


I would think that the class attribute lookup would be slower than
calling C math function.  This would defeat the original question for
speed.

For speed, write the table lookup or approximation in C.

---William Park, Open Geometry Consulting




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