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

Subject: Re: [Boost-users] Multiplying a matrix and vector ===> vector
From: Oswin Krause (Oswin.Krause_at_[hidden])
Date: 2012-10-29 06:42:59

doesn't work is a perfect error description.

On 2012-10-29 11:30, Vipin Varma wrote:
> 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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