# Boost Users :

From: yanyaqin (tinyfat_at_[hidden])
Date: 2004-09-02 18:56:32

```Thank you very much!But what's the function of ublas::permutation_matrix<size_type> pm(A.size1());And I note that there's sparse matrix and symmetric matrix type in ublas, but how can Iexpress symmetric sparse matrix conveniently?Also I want to know the performance of ublas::lu_* comparing with other math library.Best regards!Yan Yaqin 2004-09-03
----- Original Message -----
From:  "Angus Leeming"
To:  Sent: 2004-09-03 03:07:31
Subject: [Boost-users] Re: There's someone using boost lu_substitute?
>yanyaqin wrote:>>> Hi folks,
>> I'm ready to use boost lu_substitute for solving sparse symmetric linear
>> equation, but the document for lu.hpp is almost none. Is there someone
>> could provide me a real number demo?>>  >> Best regards!
>> Yan Yaqin 2004-09-02>>Hi, Yan Yaqin>
>attached is a simple example that use lu_substitute et al to calculate the
>length of each spring in a system of 10 springs arranged in series:>
>        |------o------o--- ~ ---o------o------|>
>where each spring has a random stiffness in the range 0.8 <= k <= 1.2
>>\$ g++ -I\$HOME/boost/1_31_0 -o mesh mesh.cpp>\$ ./mesh
>Node[0] position: 0>Node[1] position: 0.864606, element length: 0.864606
>Node[2] position: 1.93203, element length: 1.06742
>Node[3] position: 3.14607, element length: 1.21404
>Node[4] position: 4.03935, element length: 0.893288
>Node[5] position: 5.02106, element length: 0.981706
>Node[6] position: 5.96605, element length: 0.94499
>Node[7] position: 6.95916, element length: 0.993113
>Node[8] position: 8.02025, element length: 1.06109
>Node[9] position: 9, element length: 0.979749>
>Note that the code doesn't run when compiled against current Boost CVS
>because of a bug introduced to the Ublas library yesterday.>>Regards,
>Angus>```
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