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Filipe_Oliveira
Beginner
225 Views

Intel MKL CSR -> BSR examples in C

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Hi there,

I am having some memory problems regarding the conversion of a CSR matrix to BSR. 

Can anyone tell me some links/books/examples regarding that MKL functionality?

Thank you in advance,

Filipe Oliveira

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1 Solution
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Hi,

Have you try csr2bsr converter via new Inspector-executor SparseBlas API? The pseusocode for this converter could be represented by following scheme:

 

    sparse_status_t status;
    sparse_matrix_t  A_csr, A_bsr;

    status = mkl_sparse_d_create_csr ( &A_csr, SPARSE_INDEX_BASE_ZERO, m, n, ia, ia+1, ja, val );

    status = mkl_sparse_convert_bsr ( A_csr,   mblk, SPARSE_LAYOUT_ROW_MAJOR, SPARSE_OPERATION_NON_TRANSPOSE, &A_bsr );

    MKL_INT rows=0, cols=0, *ib, *rows_end, *jb, block_size;

    sparse_index_base_t    indexing; 
    sparse_layout_t        block_layout;
    double *b;

    status = mkl_sparse_d_export_bsr ( A_bsr, &indexing, &block_layout, &rows, &cols, &block_size, &ib, &rows_end, &jb, &b);

Thanks,

Alex

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mecej4
Black Belt
225 Views

In the CSR representation, only the non-zero elements are stored (exception: some routines may require that zero-value elements on the main diagonal should be stored).  In the BSR representation, only non-zero blocks are stored.

Thus, if the block-size = 1, the two representations are similar in storage requirements. When the block-size is not equal to 1, on the other hand, if there is at least one non-zero element in any block, all the elements in that block need to be stored (block-wise, it is "store all or none" rule that has to be followed).

As the block-size is increased, the number of within-block zeros that have to be kept will increase. Finally, when the block-size becomes equal to the matrix size, n, the entire n2 elements of the n X n full matrix will have to be kept even in the BSR representation.

I hope that you see now why the memory footprint of a BSR matrix increases when the block-size is increased.

Gennady_F_Intel
Moderator
225 Views

pls have a look at the <mkldirectory>\examples\spblasc\source\dconverters.c  example.   

//* TASK 5    Obtain block sparse row matrix from compressed sparse row matrix

Filipe_Oliveira
Beginner
225 Views

hi there,

thank you for the quick reply. is there any limitation regarding the matrix dimension in CSR format? does it need to squared in order to be convertible to BSR? 

i am also getting an strange output of the mkl_scsrbsr(...) conversion. the float *absr array is returning empty even with the correct job config:

job[0] = 0;  //If job[0]=0, the matrix in the CSR format is converted to the BSR format;

168   job[1] = 0;  //If job[1]=0, zero-based indexing for the matrix in CSR format is used;

169   job[2] = 0;  //If job[2]=0, zero-based indexing for the matrix in the BSR format is used;

170   job[3] = 0;  //

171   job[4] = 0;  //

172   job[5] = 1;  //If job[5]>0, all output arrays absr, jab, and iab are filled in for the

 

regards,

Filipe Oliveira

226 Views

Hi,

Have you try csr2bsr converter via new Inspector-executor SparseBlas API? The pseusocode for this converter could be represented by following scheme:

 

    sparse_status_t status;
    sparse_matrix_t  A_csr, A_bsr;

    status = mkl_sparse_d_create_csr ( &A_csr, SPARSE_INDEX_BASE_ZERO, m, n, ia, ia+1, ja, val );

    status = mkl_sparse_convert_bsr ( A_csr,   mblk, SPARSE_LAYOUT_ROW_MAJOR, SPARSE_OPERATION_NON_TRANSPOSE, &A_bsr );

    MKL_INT rows=0, cols=0, *ib, *rows_end, *jb, block_size;

    sparse_index_base_t    indexing; 
    sparse_layout_t        block_layout;
    double *b;

    status = mkl_sparse_d_export_bsr ( A_bsr, &indexing, &block_layout, &rows, &cols, &block_size, &ib, &rows_end, &jb, &b);

Thanks,

Alex

View solution in original post

Filipe_Oliveira
Beginner
225 Views

 

 

Alexander Kalinkin (Intel) wrote:

Hi,

Have you try csr2bsr converter via new Inspector-executor SparseBlas API? The pseusocode for this converter could be represented by following scheme:

 

    sparse_status_t status;
    sparse_matrix_t  A_csr, A_bsr;

    status = mkl_sparse_d_create_csr ( &A_csr, SPARSE_INDEX_BASE_ZERO, m, n, ia, ia+1, ja, val );

    status = mkl_sparse_convert_bsr ( A_csr,   mblk, SPARSE_LAYOUT_ROW_MAJOR, SPARSE_OPERATION_NON_TRANSPOSE, &A_bsr );

    MKL_INT rows=0, cols=0, *ib, *rows_end, *jb, block_size;

    sparse_index_base_t    indexing; 
    sparse_layout_t        block_layout;
    double *b;

    status = mkl_sparse_d_export_bsr ( A_bsr, &indexing, &block_layout, &rows, &cols, &block_size, &ib, &rows_end, &jb, &b);

Thanks,

Alex

hi there, 

is there any relation between mblk and possible memory leaks or incorrect memory acesses? because depending on the block size i get sometimes segmentation fault errors in mkl_sparse_convert_bsr

Also, is there any mkl debugging tool  in OS X?

thank you in advance,

 

225 Views

Hi,

mblk have to be divider of nrows and ncols. In this case could I ask you to send reproducer of this issue to me to understand reason of memory leaks/segfault?

Thanks,

Alex 

Filipe_Oliveira
Beginner
225 Views

Alexander Kalinkin (Intel) wrote:

mblk have to be divider of nrows and ncols. 

 

could you please rephrase this part?

If our matrix is  M rows by N columns, our mblk is n*m, N = k*n (k integer), and M = j*m (j integer), does k need to have the same value as j? 

Regards,

Filipe Oliveira and Sérgio Caldas

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