Does petsc exploit the symmetric property of matrix?

[Shengyong]

Hi, hong

Thanks very much!

Best Regards,

On Fri, Aug 15, 2008 at 10:28 PM, Hong Zhang <hzhang at mcs.anl.gov> wrote:

>
> Shengyong,
>
> On Fri, 15 Aug 2008, berry wrote:
>
>  Hi,
>>
>> I am totally a newbie to petsc. Previously I use laspack library for my
>> linear solver. Now I decide to transfer to Petsc for our simulation code.
>>
>> I have a huge sparse matrix with 3million*3million with 21 million no zero
>> elements.  The matrix is symmetric, so the non zero element of upper
>> triangular matrix
>> is only 12 million.  And matrix format is Yale Space Matrix format.
>> However,
>> I have not seen any indicative parmater for matrix symmetry property in
>> MatCreateSeqAIJWithArrays() function.  The manual says:
>>
>>
>> PetscErrorCode PETSCMAT_DLLEXPORT MatCreateSeqAIJWithArrays(MPI_Comm
>> comm,PetscInt m,PetscInt n,PetscInt* i,PetscInt*j,PetscScalar *a,Mat
>> *mat)
>>
>> <
>> http://www-unix.mcs.anl.gov/petsc/petsc-2/snapshots/petsc-current/docs/manualpages/Sys/MPI_Comm.html#MPI_Comm
>> >
>>
>> Input Parameters
>> *comm<
>> http://www-unix.mcs.anl.gov/petsc/petsc-2/snapshots/petsc-current/docs/manualpages/Sys/comm.html#comm
>> >
>> *- must be an MPI communicator of
>> size<
>> http://www-unix.mcs.anl.gov/petsc/petsc-2/snapshots/petsc-current/docs/manualpages/Sys/size.html#size
>> >1
>> *m *- number of rows
>> *n *- number of columns
>> *i *- row indices
>> *j *
>>
>> *a *
>>
>>
>> Can petsc exploit any symmetric proptery of a given matrix?  How could I
>> Set
>> it to be symmetry one ?
>>
>
> You can use MATSBAIJ matrix format
> (see
> http://www-unix.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MATSBAIJ.html
> )
>
> Using MATSBAIJ saves half of storage space for original sparse matrix.
> However,
> it is not as efficient as MATAIJ for some matrix operations, e.g.,
> MatMult(), due to non-contiguous data access and additional communication
> overhead.
>
> Hong
>
>
>> Best Regards,
>>
>>
>>
>>
>> --
>> Pang Shengyong
>> Solidification Simulation Lab,
>> State Key Lab of Mould & Die Technology,
>> Huazhong Univ. of Sci. & Tech. China
>>
>>
>


-- 
Pang Shengyong
Solidification  Simulation Lab,
State Key Lab of  Mould & Die Technology,
Huazhong Univ. of Sci. & Tech. China
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