[Insight-users] solving large linear equations

[Habib Baluwala]

Hi Arnaud, 
               The size of the matrix is around 40,000 rows and columns but
the density is around 5 percent which is very small. I am using the
vnl_sparse_matrix for reading the sparse matrix and then using the
vnl_sparse_lu and for solving the equations. I thought that the blas and
lapack libraries are linked with the linear solver but that does not seem to
be the case or I am currently not using any pointers for the sparse matrix.
Can this be a reason for the failure????? I look forward to yor reply 





Arnaud Gelas wrote:
> 
> Hi habbib,
> 
> How large is your matrix?
> How sparse is your matrix? Do you know the number of non null elements 
> in your matrix? Or can you tell me the number of non null elements per 
> row (in average)?
> 
> Solving sparse linear system highly depends on the sparsity of your
> matrix.
> When you say I am "using VNL sparse system solver", what do you mean? 
> which class are you using?
> 
> Note that it is not because you use BLAS and LAPACK that the code will 
> be fast, it depends how they are used in in the library. For example 
> mumps, taucs are also based on blas and lapack and performances are 
> really different...
> 
> Arnaud
> 
> Habib Baluwala wrote:
>> Hi everyone , 
>>                  I am currently using a large sparse system of linear
>> equation which is non-symmetric. I tried using VNL sparse system solvers
>> but
>> they are very slow , I can't still understand why they are slow because
>> they
>> are supposed to utilise the BLAS and Lapack libraries to speed up. Can
>> anyone tell me how can I speed up the procedure???? I also tried the
>> release
>> instead of debug. It was able to reduce the time taken but not to a
>> significant effect. Would including the Utilities folder in the
>> CMakeFile.txt help ???
>>
>> I look forward to your reply and sorry for any inconvenience. 
>>
>>
>>
>>   
> 
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