prod doesn't work with matrix and compressed_matrix

[albertz]

Code:

// c++ test_prod_sparse.cpp  -std=c++11

#include <viennacl/vector.hpp>
#include <viennacl/matrix.hpp>
#include <viennacl/compressed_matrix.hpp>
#include <viennacl/linalg/prod.hpp>
#include <viennacl/linalg/vector_operations.hpp>
#include <viennacl/linalg/matrix_operations.hpp>
#include <viennacl/scalar.hpp>
#include <viennacl/matrix_proxy.hpp>

int main() {
    using namespace viennacl;
    using namespace viennacl::linalg;

    auto a = matrix<float>(10,10);
    auto b = compressed_matrix<float>(10,10);
    auto v = prod(a, b);

    return 0;
}

Error:

az@azmacbookpro ~/P/N/NN-OCR> c++ test_prod_sparse.cpp  -std=c++11
test_prod_sparse.cpp:18:11: error: no matching function for call to 'prod'
        auto v = prod(a, b);
                 ^~~~
/usr/local/include/viennacl/linalg/prod.hpp:91:5: note: candidate template
      ignored: failed template argument deduction
    prod(std::vector< std::vector<T, A1>, A2 > const & matrix, VectorT c...
    ^
/usr/local/include/viennacl/linalg/prod.hpp:106:5: note: candidate template
      ignored: failed template argument deduction
    prod(std::vector< std::map<KEY, DATA, COMPARE, AMAP>, AVEC > const& ...
    ^
/usr/local/include/viennacl/linalg/prod.hpp:142:5: note: candidate template
      ignored: failed template argument deduction
    prod(viennacl::matrix_base<NumericT, F1> const & A,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:158:5: note: candidate template
      ignored: failed template argument deduction
    prod(viennacl::matrix_base<NumericT, F1> const & A,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:178:5: note: candidate template
      ignored: failed template argument deduction
    prod(viennacl::matrix_expression<const viennacl::matrix_base<NumericT, F1>,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:201:5: note: candidate template
      ignored: failed template argument deduction
    prod(viennacl::matrix_expression<const viennacl::matrix_base<NumericT, F1>,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:225:5: note: candidate template
      ignored: failed template argument deduction
    prod(viennacl::matrix_base<NumericT, F> const & matrix,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:241:5: note: candidate template
      ignored: failed template argument deduction
    prod(viennacl::matrix_expression<const viennacl::matrix_base<NumericT, F>,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:261:5: note: candidate template
      ignored: failed template argument deduction
    prod(const SparseMatrixType & mat,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:275:5: note: candidate template
      ignored: failed template argument deduction
    prod(const SparseMatrixType & sp_mat,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:292:5: note: candidate template
      ignored: failed template argument deduction
    prod(const SparseMatrixType & A,
    ^
/usr/local/include/viennacl/linalg/prod.hpp:310:5: note: candidate template
      ignored: failed template argument deduction
    prod(const StructuredMatrixType & mat,
    ^
1 error generated.

[karlrupp]

So far we only support a sparse first factor, i.e. in C = prod(A, B); only A can be sparse, not B or C. This has performance reasons, because one can only iterate quickly along rows of a sparse matrix, not along columns.

prod(B, A) with sparse A will only work reasonably well if the cost of transposing A in memory is substantially smaller than the cost of prod(B, A') where A' is the same as A but stored in column-major layout.