Re: [ojAlgo-user] Performance tests

[Anders P. <ap...@op...>]

Niko Brummer wrote:
> Hi Anders
>
> I have a general comment about  performance when working with large matrices.
>
> ************************************************************************
> *  It matters a lot in what order you access the data in memory. *
> ************************************************************************
>   
> I have done similar matrix multiplication experiments in Java, with
> similar results. Although in Java you don't have very good control
> over how and where matrix elements are stored in memory, it is still
> often possible by re-arranging the order in which elements are
> accessed, to speed up things considerably.

I have spent many hours performance tweaking ojAlgo. (Performance has 
improved a lot with the last handful of releases.) Though I am beginning 
to get a feeling for what is good/bad I cannot say I know how to write 
top performing code. I have to experiment, and tiny changes can make a 
huge difference. Yes, I have also learned, that thinking about in what 
order you access array elements is very important. Doing matrix 
decompositions, in place, is particularly difficult.

/Anders