Re: [ublas] Subrange or slice on sparse matrices

Subject: Re: [ublas] Subrange or slice on sparse matrices
From: Umut Tabak (u.tabak_at_[hidden])
Date: 2008-11-30 08:22:57

Gunter Winkler wrote:
> Am Freitag, 28. November 2008 01:07 schrieb Umut Tabak:
>   
>> Dear all,
>>
>> While planning for some possible fe code generation, I tried to check
>> the Ublas lib. I was wondering if subrange/slice capabilities also
>> apply to sparse matrices? Or are there some tricks or workarounds to
>> make this happen?
>>     
>
> The range and slice operation work with all matrix types - including 
> sparse ones.
>
> simply use project():
>
> compressed_matrix<double> A(50000, 50000);
> vector<double> x(5);
> y = prod(project(A, range(0,50000), range(1000,1005)), x);
>
> or
>
> apxy_prod(project(A, range(0,50000), range(1000,1005)), x, y, false);
> (which is more efficient ...)
>
> mfg
> Gunter
>
> PS: However uBLAS default algorithms can still be beaten by handcoded, 
> optimized routines, see http://guwi17.de/ublas/matrix_sparse_usage.html
>
> mfg
> Gunter
>   
>   
As a newcomer, this was what I was looking... Thx
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>   

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