Re: [ublas] Matrix Trace?

From: Nico Galoppo (nico_at_[hidden])
Date: 2007-06-12 01:17:36

Sorry about the typo, that should obviously be

matrix_type m(n,n);
matrix_vector_range<matrix_type> diag(m, range (0,n), range (0,n));
double trace = sum(diag);

--nico

Nico Galoppo wrote:
> Markus,
> 
> you can get the diagonal of a square matrix m as a vector expression like this:
> 
> matrix_type m(n,n);
> matrix_vector_range<matrix_type> diag(m, range (0,n), range (0,n));
> 
> Then the trace is just the sum of the elements:
> 
> double trace = sum(mvs);
> 
> --nico
> 
> Markus Weimer wrote:
>> Hi,
>>
>> I have some legacy code that computes the inner product between two 
>> row-major matrices by treating them as long vectors and applying a 
>> vector inner product to these vectors. I guess getting a vector-view 
>> onto a matrix is not possible in uBLAS. Thus, I want to compute the 
>> inner product between two matrices as follows:
>>
>> v = tr(A*B)
>>
>> However, I cannot find the trace operation in the documentation. Does 
>> that mean that there is no trace in uBLAS?
>>
>> Thanks in advance,
>>
>> Markus
>>
>>
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>>
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> 

-- 
Nico Galoppo        UNC-CH PhD. student        http://www.ngaloppo.org
                       [phone]