Re: [ViennaCL-support] Append a vector to a matrix row

[Karl R. <ru...@iu...>]

Hi Kirell,

if you're using OpenCL, there's a way for promoting a vector to a matrix 
as follows:

vector<double> x = prod(A, y); // this is your SpMV operation

// create the proxy object. Adjust num_cols, num_rows is probably 1
matrix<double> x2(x.handle().opencl_handle(), num_rows, num_cols);

your_range += x2;   //here you add to your subrange


This currently doesn't work with CUDA or the OpenMP backends, though.

Best regards,
Karli



On 05/15/2013 10:48 AM, Kirell Benzi wrote:
> Hi,
> In append I mean setting the entries.
>
> something like this:
>
> matrix.at(row) += myVector;
>
> I have tried to create the vector as a matrix, but this vector is the result of of compressed_matrix * vector. The sparse matrix * matrix is not implemented is viennacl, so I need to transform my vector in a matrix.
>
> The other solution would be to have a std::vector< viennacl:::vector> > instead of a matrix. But it will be slow since for each operation I would have to switch back and forth with the cpu_ram.
>
> Do you have any advices ?
>
> ++
>
> ----------------------------------------------------------------------
>
> Kirell Benzi
> PhD student, Research assistant,
> Laboratoire de traitement des signaux 2
> Institute of Electrical Engineering - IEL
> Ecole Polytechnique Fédérale de Lausanne - EPFL
> EPFL/STI/IEL/LTS2
> ELE 229 (Bâtiment ELE)
> Station 11
> CH-1015 Lausanne
> Switzerland
> Home page: http://people.epfl.ch/kirell.benzi
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> Tel: +41 21 69 37895
> ----------------------------------------------------------------------
>
> On 15 mai 2013, at 17:40, Karl Rupp <ru...@iu...>
>   wrote:
>
>> Hi Kirell,
>>
>>> I'm new to viennacl.
>>> I want to add a row vector to a specific row of in matrix.
>>> I have created a matrix_range in a for loop to specify the row I want.
>>> Unfortunately, I cannot append a vector to a matrix range.
>>>
>>> I have tried to transform my vector to a matrix, but it seems impossible.
>>
>> what exactly do you mean by 'append'? Should a NxN-matrix become a (N+1)xN-matrix, or do you just want to set the entries?
>>
>> In the former case, you need to resize() the matrix and refill it. In the latter case you currently need to create the 'vector' as a 1xN or 1xM-matrix and then assign to the matrix-range. We don't yet have the generic row() and column() functions ready to directly assign vectors to a matrix row/column.
>>
>> Best regards,
>> Karli
>
>