HOW TO OUTPUT SYSTEM MATRIX IN A FILE

[孙翔]

Hi, I followed step-17 and build a system matrix of which type is PETScWrappers::MPI::SparseMatrix. I want to output it after assembling. How should I do it? Thank you very much. 

Best,

Xiang

[Wolfgang Bangerth]

If performance doesn't matter, just loop over all indices i and j and output
the value of the matrix. If you're running in parallel, you need to restrict
the loop over i to the locally owned range.

Best
W.


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Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/

[Daniel Arndt]

Of course, there is also PETScWrappers::MatrixBase::print(https://www.dealii.org/current/doxygen/deal.II/classPETScWrappers_1_1MatrixBase.html#a7515e640202d1ad50bd9baa13c404cb1) that should work.

Best,

Daniel

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[Wolfgang Bangerth]

On 7/29/20 1:31 PM, Daniel Arndt wrote:
> Of course, there is also
> PETScWrappers::MatrixBase::print(https://www.dealii.org/current/doxygen/deal.II/classPETScWrappers_1_1MatrixBase.html#a7515e640202d1ad50bd9baa13c404cb1

> <https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.dealii.org%2Fcurrent%2Fdoxygen%2Fdeal.II%2FclassPETScWrappers_1_1MatrixBase.html%23a7515e640202d1ad50bd9baa13c404cb1&data=02%7C01%7CWolfgang.Bangerth%40colostate.edu%7C741ab88a0bde4381989208d833f5fe8c%7Cafb58802ff7a4bb1ab21367ff2ecfc8b%7C0%7C0%7C637316478913030640&sdata=sOoVCUSnTWzX10j0pVHnVUHeafeQV4DWkEYAkjrqZAo%3D&reserved=0>)
> that should work.

Ah, yes, that's much better!

[孙翔]

Thank you very much. 

[孙翔]

Thank you very much. 

On Wednesday, 29 July 2020 12:31:30 UTC-7, Daniel Arndt wrote:

Of course, there is also PETScWrappers::MatrixBase::print(https://www.dealii.org/current/doxygen/deal.II/classPETScWrappers_1_1MatrixBase.html#a7515e640202d1ad50bd9baa13c404cb1) that should work.

Best,

Daniel

Am Mi., 29. Juli 2020 um 12:59 Uhr schrieb Wolfgang Bangerth <bang...@colostate.edu>:

On 7/28/20 12:11 PM, 孙翔 wrote:
> Hi, I followed step-17 and build a system matrix of which type
> is PETScWrappers::MPI::SparseMatrix. I want to output it after assembling. How
> should I do it? Thank you very much.

If performance doesn't matter, just loop over all indices i and j and output
the value of the matrix. If you're running in parallel, you need to restrict
the loop over i to the locally owned range.

Best
  W.


--
------------------------------------------------------------------------
Wolfgang Bangerth          email:                 bang...@colostate.edu
                            www: http://www.math.colostate.edu/~bangerth/

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