Is this the correct way to use MatGetRow? Something wrong here

[Ben Tay]

Thanks Zhang Hong!

I've got it working.

Hong Zhang wrote:
> See ~petsc/src/mat/examples/tests/ex58f.F on
> how to use MatGetRow() from Fortran.
>
> Hong
>
> On Mon, 27 Aug 2007, Ben Tay wrote:
>
>   
>> Hi,
>>
>> I'm trying to view a particular row of a matrix. This 's what I do in my
>> loops:
>>
>> real(8):: vector(64)
>>
>> II=36
>>
>> impl_mat_i=4.
>>
>> call MatSetValue(A_mat_uv,II,II,impl_mat_i,ADD_VALUES,ierr)
>>
>> call MatAssemblyBegin(A_mat_uv,MAT_FINAL_ASSEMBLY,ierr)
>>
>> call MatAssemblyEnd(A_mat_uv,MAT_FINAL_ASSEMBLY,ierr)
>>
>>
>> call MatGetRow(A_mat_uv,II,PETSC_NULL,PETSC_NULL,vector,ierr)
>>
>> call MatRestoreRow(A_mat_uv,II,PETSC_NULL,PETSC_NULL,vector,ierr)
>>
>> When I look at "vector" using visual fortran debugger, I saw many
>> different values in it, but I only added 1 value in 1 location. However,
>> just before I use MatSetValue, I also called MatGetRow. It was initially
>> all zero.
>>
>> But, if I use call
>> MatSetValue(A_mat_uv,II,*1*,impl_mat_i,ADD_VALUES,ierr) instead of II, I
>> see only 4 in vector(1).
>>
>> What happening? Where did all the other values come from? Also, is this
>> the best way to view a particular row of a matrix? I tried to use
>>
>> call MatGetValues(A_mat_uv,1,36,64,1,vector,ierr) to get 1 row of values
>> from the 36th row.There are 64 columns in total. Seems like it's the
>> wrong way. Can you please show me the correct way?
>>
>> Thank you.
>>
>>
>>     
>
>
>