[petsc-users] Using MatSetValues to add all matrix values in 1 run

[TAY wee-beng]

On 1/10/2012 4:39 PM, Jed Brown wrote:
> MatSetValues() inserts logically dense blocks. You are thinking of it 
> as inserting a bunch of arbitrary (row,col,value) but that's not how 
> it works. Read the man page and look at any of the examples.

If that's the case, is the 1st method I used the best way to insert the 
matrix?

In other words, I already have the A matrix and b vector in Fortran 
matrix, used for solving Ax = b.

Is there a better or more efficient way of inserting the Fortran matrix 
into PETSC's matrix?

Thanks
>
> On Mon, Oct 1, 2012 at 10:36 AM, TAY wee-beng <zonexo at gmail.com 
> <mailto:zonexo at gmail.com>> wrote:
>
>     Hi,
>
>     I'm trying to insert values into my PETSc matrix using MatSetValues.
>
>     I tried using:
>
>     /do ijk=ijk_xyz_sta,ijk_xyz_end//
>     //
>     //    II = ijk - 1    !Fortran shift to 0-based//
>     ////
>     //    call
>     MatSetValues(A_semi_xyz,1,II,7,int_semi_xyz(ijk,1:7),semi_mat_xyz(ijk,1:7),INSERT_VALUES,ierr)//
>     //
>     //end do/
>
>     where ijk_xyz_sta/ijk_xyz_end are the starting/end index
>
>     int_semi_xyz(ijk,1:7) stores the 7 column global indices
>
>     semi_mat_xyz has the corresponding values.
>
>     This work well but I'm trying to call MatSetValues in 1 statement,
>     it failed. I tried:
>
>     /do ijk = 1,ijk_xyz_end-ijk_xyz_sta//
>     //
>     //    rows(ijk) = ijk_xyz_sta + ijk - 1//    !to get row's global
>     indices
>     ////
>     //end do//
>     //
>     //call
>     MatSetValues(A_semi_xyz,ijk_xyz_end-ijk_xyz_sta,rows,7,int_semi_xyz(ijk_xyz_sta+1:ijk_xyz_end,1:7),semi_mat_xyz(ijk_xyz_sta+1:ijk_xyz_end,1:7),INSERT_VALUES,ierr)/
>
>     but when I use MatView, the values are in the wrong locations.
>
>     May I know what's wrong?
>
>     Thanks
>
>     -- 
>     Yours sincerely,
>
>     TAY wee-beng
>
>

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