[petsc-users] Problem with fortran version of ex29 in ksp

[Matthew Knepley]

On Wed, May 2, 2012 at 1:55 PM, TAY wee-beng <zonexo at gmail.com> wrote:

>  Hi,
>
> I did a MatView and VecView on both C and Fortran, right after Mat and Vec
> assembly. I have attached the printout below. They are exactly the same,
> but yet the result is different in Neumann condition. However, the
> dirichlet condition gives the correct ans. Is there anything else that
> could be wrong even if the Mat and Vec are the same?
>

Did you set the null space for the matrix when you have Neumann conditions?

   Matt


> Thanks!
>
> Fortran:
>
> Matrix Object: 1 MPI processes
>   type: seqaij
> row 0: (0, 2)  (1, -1)  (3, -1)
> row 1: (0, -1)  (1, 3)  (2, -1)  (4, -1)
> row 2: (1, -1)  (2, 2)  (5, -1)
> row 3: (0, -1)  (3, 3)  (4, -1)  (6, -1)
> row 4: (1, -1)  (3, -1)  (4, 4)  (5, -1)  (7, -1)
> row 5: (2, -1)  (4, -1)  (5, 3)  (8, -1)
> row 6: (3, -1)  (6, 2)  (7, -1)
> row 7: (4, -1)  (6, -1)  (7, 3)  (8, -1)
> row 8: (5, -1)  (7, -1)  (8, 2)
> Vector Object:Vec_0000000084000000_0 1 MPI processes
>   type: mpi
> Process [0]
> 0.25
> 0.0205213
> 1.135e-005
> 0.0205213
> 0.00168449
> 9.31663e-007
> 1.135e-005
> 9.31663e-007
> 5.15289e-010
> Vector Object:Vec_0000000084000000_1 1 MPI processes
>   type: mpi
> Process [0]
> 0.14924
> 0.0242397
> -0.0260347
> 0.0242397
> -0.0256192
> -0.0400102
> -0.0260347
> -0.0400102
> -0.0400102
> Press any key to continue . . .
>
> C:
>
> Matrix Object: 1 MPI processes
>   type: seqaij
> row 0: (0, 2)  (1, -1)  (3, -1)
> row 1: (0, -1)  (1, 3)  (2, -1)  (4, -1)
> row 2: (1, -1)  (2, 2)  (5, -1)
> row 3: (0, -1)  (3, 3)  (4, -1)  (6, -1)
> row 4: (1, -1)  (3, -1)  (4, 4)  (5, -1)  (7, -1)
> row 5: (2, -1)  (4, -1)  (5, 3)  (8, -1)
> row 6: (3, -1)  (6, 2)  (7, -1)
> row 7: (4, -1)  (6, -1)  (7, 3)  (8, -1)
> row 8: (5, -1)  (7, -1)  (8, 2)
> Vector Object:Vec_0x1d3b000_0 1 MPI processes
>   type: mpi
> Process [0]
> 0.25
> 0.0205212
> 1.135e-05
> 0.0205212
> 0.00168449
> 9.31663e-07
> 1.135e-05
> 9.31663e-07
> 5.15288e-10
> Vector Object:Vec_0x1d3b000_1 1 MPI processes
>   type: mpi
> Process [0]
> 0.139311
> 0.0305751
> -0.0220633
> 0.0305751
> -0.0135158
> -0.042185
> -0.0220633
> -0.042185
> -0.058449
>
>
>
> Yours sincerely,
>
> TAY wee-beng
>
>
> On 1/5/2012 11:54 PM, Matthew Knepley wrote:
>
> On Tue, May 1, 2012 at 5:48 PM, TAY wee-beng <zonexo at gmail.com> wrote:
>
>> Hi,
>>
>> Do you mean my method is wrong?
>>
>> I am following the template of ex22f,
>>
>> where the variables are declared as :
>>
>> PetscScalar  v(5)
>>
>> MatStencil   row(4),col(4,5)
>>
>> Hence,
>>
>> for the neumann BC
>>
>> num = 1
>>
>>                if (j/=0) then
>>
>>                    v(num) = -rho*HxdHy
>>
>>                    col(MatStencil_i,num) = i
>>
>>                    col(MatStencil_j,num) = j-1
>>
>>                    num = num + 1
>>
>>                end if
>>
>>                if (i/=0) then
>>
>>                    v(num) = -rho*HydHx
>>
>>                    col(MatStencil_i,num) = i-1
>>
>>                    col(MatStencil_j,num) = j
>>
>>                    num = num + 1
>>
>>                end if
>>
>>                if (i/=mx-1) then
>>
>>                    v(num) = -rho*HydHx
>>
>>                    col(MatStencil_i,num) = i+1
>>
>>                    col(MatStencil_j,num) = j
>>
>>                    num = num + 1
>>
>>                end if
>>
>>                if (j/=my-1) then
>>
>>                    v(num) = -rho*HxdHy
>>
>>                    col(MatStencil_i,num) = i
>>
>>                    col(MatStencil_j,num) = j+1
>>
>>                    num = num + 1
>>
>>                end if
>>
>>                v(num) = ((num-1)/2.0)*rho*(HxdHy + HydHx)
>>
>>                print *, v
>>
>>                col(MatStencil_i,num) = i
>>
>>                col(MatStencil_j,num) = j
>>
>>                !num = num + 1
>>
>>                call
>> MatSetValuesStencil(jac,i1,row,num,col,v,INSERT_VALUES,ierr)
>>
>> I do not get any more out of range error. However,my ans is still
>> different from that of ex29 in C.
>>
>
>  This is very simple. You have an error in your code. Checking it is very
> simple: run the code and
> break in MatSetValues(). Make sure ex29 makes calls with exactly the same
> indices as your ex29f.
>
>      Matt
>
>
>> Yours sincerely,
>>
>> TAY wee-beng
>>
>
>  --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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