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

Subject: Re: [Boost-users] Multiplying a matrix and vector ===> vector
From: Vipin Varma (varma_at_[hidden])
Date: 2012-10-29 06:30:11

That worked but only with a boost::ublas::numeric::compressed_vector and 
not a simple boost::ublas::numeric::vector.

Thanks,
Vipin

On Sun, 28 Oct 2012, Oswin Krause wrote:

> Hi,
>
> without knowing what CLN should be (would have been nice to know beforehand, 
> that you are using an unusual value_typ for vectors/matrics...)
>
> I suspect you are compiling in debug mode and the error goes away in release. 
> This is because the debug test for numeric stability fails.
>
> Try to define this before including anything from ublas (or set as compile 
> flag):
> BOOST_UBLAS_TYPE_CHECK=0
>
> On 2012-10-27 11:47, Vipin Varma wrote:
>> 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<compressed_matrix, vector, ?
>>>>> 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_at_[hidden]
>>>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>>> 
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