[SciPy-user] Getting the right numerical libraries for scipy

David Cournapeau david@ar.media.kyoto-u.ac...
Fri Apr 3 09:12:24 CDT 2009


David Cournapeau wrote:
>
> I think it will depend on your dot implementation (does it uses atlas or
> other heavily optimized implementation). This is to be taken with a
> (big) grain of salt since I don't know much about sparse matrices, but
> if the distribution is purely random, then I can see how sparse matrices
> would be much slower than contiguous arrays. Memory access is often the
> bottleneck for simple FPU operations on big data, and random memory
> access just kills access performances  (can be order of magnitude slower
> - a cache miss on modern CPU costs ~ 250 cycles).
>   

Sorry, there lacks one sentence here: memory access patterns for sparse
matrices are more difficult to optimize than plain arrays.

cheers,

David


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