[petsc-users] Convert matrix to 1-D array

[priyank patel]

hi,

Ya this will give me only local entries. But what if I want the complete matrix in one array. So that I can use it with the lapack routines??

Thanks
Priyank

On 19-Aug-2014, at 2:09 pm, Hong <hzhang at mcs.anl.gov> wrote:

> Priyank:
> The product C = A * B is a dense matrix in petsc mpidense format.
> You should use MatDenseGetArray()
> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatDenseGetArray.html
> 
> which gives 1D array of local entries of C.
> 
> I notice you are using petsc-3.3. Please update to the latest version of petsc.
> 
> Hong
> 
>> Hello,
>> 
>> I have a matrix generated from matrix matrix multiplication. I want that
>> matrix to convert to 1 dimensional array. my code is as below
>> 
>> #####################################################
>> //Multiplication A * B (A is MPIAIJ & B is MPIDENSE)
>> MatMatMult(A, B,  MAT_INITIAL_MATRIX,  PETSC_DEFAULT, &C);
>> MatView(C,PETSC_VIEWER_STDOUT_WORLD);
>> //Convert Matrix C to 1D vector h_C
>> for(i = 0; i < m; i++)
>> {
>> for(j = 0; j < k; j++)
>> {
>> ierr = MatGetValues(C, 1, &i, 1, &j, &h_C[IDX2C(i,j,end1)]);CHKERRQ(ierr);
>> }
>> }
>> //printArray(h_B, m, k, "h_B");
>> printArray(h_C, m, k, "A * X0");
>> #####################################################
>> when I tried the routine MatGetValues() it shows some error as below
>> 
>> #####################################################
>> --------------------- Error Message ------------------------------------
>> [1]PETSC ERROR: No support for this operation for this object type!
>> [1]PETSC ERROR: Only local values currently supported!
>> [1]PETSC ERROR:
>> ------------------------------------------------------------------------
>> [1]PETSC ERROR: Petsc Release Version 3.3.0, Patch 0, Tue Jun  5 14:20:42
>> CDT 2012
>> [1]PETSC ERROR: See docs/changes/index.html for recent updates.
>> [1]PETSC ERROR: See docs/faq.html for hints about trouble shooting.
>> [1]PETSC ERROR: See docs/index.html for manual pages.
>> [1]PETSC ERROR:
>> ------------------------------------------------------------------------
>> [1]PETSC ERROR: ./blockCG_1 on a arch-linu named hpcd.cs.odu.edu by ppatel
>> Tue Aug 19 12:29:41 2014
>> [1]PETSC ERROR: Libraries linked from /export/software/petsc-3.3/lib
>> [1]PETSC ERROR: Configure run at Wed Jun  6 16:29:21 2012
>> [1]PETSC ERROR: Configure options --prefix=/export/software/petsc-3.3
>> --download-f-blas-lapack=1
>> [1]PETSC ERROR:
>> ------------------------------------------------------------------------
>> [1]PETSC ERROR: MatGetValues_MPIDense() line 180 in
>> src/mat/impls/dense/mpi/mpidense.c
>> [1]PETSC ERROR: MatGetValues() line 1602 in src/mat/interface/matrix.c
>> [1]PETSC ERROR: main() line 343 in blockCG_1.c
>> --------------------------------------------------------------------------
>> MPI_ABORT was invoked on rank 1 in communicator MPI_COMM_WORLD
>> with errorcode 56.
>> 
>> NOTE: invoking MPI_ABORT causes Open MPI to kill all MPI processes.
>> You may or may not see output from other processes, depending on
>> exactly when Open MPI kills them.
>> --------------------------------------------------------------------------
>> 
>> #####################################################
>> 
>> what is the efficient way to create a 1-D array from the PETSC matrix?