Re: [Boost-users] Multiplying a matrix and vector ===> vector

Yes, in fact I just realised that I can do all the usual algebra for standard data types like double, float etc. But when I try to use CLN rational numbers - which is what I want - the below step fails with the following compile error: <ERROR> /usr/include/boost/numeric/ublas/traits.hpp:97: error: no matching function for call to 'sqrt(const cln::cl_RA&)' /usr/include/bits/mathcalls.h:157: note: candidates are: double sqrt(double) /usr/include/c++/4.3/cmath:434: note: long double std::sqrt(long double) /usr/include/c++/4.3/cmath:430: note: float std::sqrt(float) <ERROR> However I can still multiply a scalar CLN number with a CLN matrix and assign it to a new CLN matrix; it's multiplication of a CLN vector with a CLN matrix that gives the problem. Thanks, Vipin On Fri, 26 Oct 2012, Oswin Krause wrote:

Have you tried:

vector z = prod(m,x);

On 2012-10-26 13:08, Vipin Varma wrote:

...

Dear all,

My basic requirement is to multiply a matrix and a vector and then to store it into a vector using Boost's UBLAS.

When I multiply a boost::numeric::ublas::compressed_matrix with a boost::numeric::ublas::vector using prod(matrix, vector), the output is a boost::numeric::ublas::matrix_vector_binary1. E.g. <PSEUDOCODE> boost::numeric::ublas::compressed_matrix m; boost::numeric::ublas::vector x; boost::numeric::ublas::matrix_vector_binary1

...

tmp; tmp = prod(m,x); <PSEUDOCODE> The problem is that in the third field --- which expects the operation type --- in line 3, I do not know what to enter or how to specify the type of operation; I tried '*' and 'prod' and 'vector' and 'compressed_matrix' but none work.

Alternatively, I can avoid the tmp variable altogether and get a working program to copy the result of matrix-vector multiplication onto a new vector y but then I would need two multiplications. E.g. <CODE> std::copy(prod(m,x).begin(), prod(m,x).end(), y.begin()); <CODE>

Any suggestions on how to declare a matrix_vector_binary1 correctly or how to get the finaly result efficiently onto a vector will be appreciated.

Regards, Vipin _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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