Re: [ublas] [bindings][traits] is_vector, is_matrix

Subject: Re: [ublas] [bindings][traits] is_vector, is_matrix
From: Karl Meerbergen (Karl.Meerbergen_at_[hidden])
Date: 2009-03-12 04:39:13

Rutger ter Borg wrote:
> Jesse Perla wrote:
>
>   
>> Speaking of which...  The bindings for ?tritri don't seem to work as one
>> would expect for triangular matrices.  The following code works:
>> ublas::matrix<double, ublas::column_major> (A2,2);
>> A(0,0) = 1.0;
>> A(1,0) = 1.0; A(1, 1) = 2.0;
>> A(0, 1) = 0.0; //Shouldn't need, but good to set
>> lapack::trtri('L', 'N', A);
>>     
>
> This is right, trtri is meant for normal dense matrices (=storage format) of
> which you say they are triangular. I've added support for uplo detection in
> trtri, to use it now please use ublas' triangular adaptor to indicate
> whether it is upper/lower. 
>
> I'm not sure whether it is possible to do the diag detection through the
> traits at the moment -- Karl?
>   

What do you mean by diag detection?

>  
>   
>> But the following won't compile, which has the triangular matrix one would
>> expect to work:
>>
>> ublas::triangular_matrix<double, ublas::lower, ublas::column_major>
>> A(2,2); A(0,0) = 1.0;
>> A(1,0) = 1.0; A(1, 1) = 2.0;
>> lapack::trtri('L', 'N', A);
>>     
>
> I think ublas uses a packed storage format for triangular matrices. Please
> try tptri, I've just added it to the computational section. However, I
> think the traits do not support triangular matrices yet?
>   

Don't they? I would hope so. A packed format is supported for sure.

Karl

>   
>> The new bindings seem to compile and my basic test cases worked.  I still
>> don't really know what is going on with the workspace stuff, but should
>> the following code (which compiles) work? (it pops out a different number
>> than matlab, but I could be misinterpreting the results):
>>
>> ublas::matrix<double, ublas::column_major> A(2,2);
>> //First need to call getrf()
>> std::vector<int> ipiv (2);  // pivot vector
>> lapack::getrf(A, ipiv);
>> //Then can get the inverse
>> lapack::getri(A, ipiv, lapack::optimal_workspace() );
>>
>> ... optimal_workspace() is compiling now, but is it working?
>>     
>
> If you would like to see what workspace size has been chosen, you could
> insert a 
>
> std::cout << "Workspace real size: " << traits::detail::to_int(
> opt_size_work ) << std::endl;
>
> at line 110/111 of getri.
>
> Cheers,
>
> Rutger
>
>
>
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