DACreate2d() and DAGetMatrix()

[(Rebecca) Xuefei YUAN]

I check the matrix.c and find that the x,y,z direction has been  
reversed as in line 1249-1252 in MatSetStencil(), can I get to know  
why we do this?

Thanks.


1249:   for (i=0; i<dim; i++) {
1250:     mat->stencil.dims[i]   = dims[dim-i-1];      /* copy the  
values in backwards */
1251:     mat->stencil.starts[i] = starts[dim-i-1];
1252:   }

Quoting "(Rebecca) Xuefei YUAN" <xy2102 at columbia.edu>:

> I think the dims should be {9,5,4,0} if it is Xperiodic, and should be
> {5,9,4,0} if it is Yperiodic. Am I right?
>
> Thanks,
>
> Rebecca
>
>
> Quoting "(Rebecca) Xuefei YUAN" <xy2102 at columbia.edu>:
>
>> If I have -da_grid_x 5 -da_grid_y 5 -dmmg_nlevels 1 and the DA and
>> jacobian like:
>>>> ierr = DMMGCreate(comm, 1, &appCtx, &dmmg);CHKERRQ(ierr);
>>>> ierr = DACreate2d(comm,DA_XPERIODIC,DA_STENCIL_STAR, -5, -5,     
>>>> PETSC_DECIDE, PETSC_DECIDE, 4, 2, 0, 0, &da);CHKERRQ(ierr);
>>>> ierr = DMMGSetDM(dmmg, (DM)da);CHKERRQ(ierr);
>>>> ierr = DAGetMatrix(DMMGGetDA(dmmg), MATAIJ, &jacobian);CHKERRQ(ierr);
>>
>> will that be right if I have jacobian->stencil.dims ={5, 9, 4, 0}?
>>
>> Thanks,
>>
>> Rebecca
>>
>>
>>
>> Quoting Barry Smith <bsmith at mcs.anl.gov>:
>>
>>>
>>>  The dof argument to DACreate2d() is greater than 1. Thus the
>>> "dimension" that is associated with the matrix is 3 dimensions.  Is
>>> this causing a problem?
>>>
>>>
>>>  Barry
>>>
>>> Note: the "dimension" of the matrix affects the MatSetValuesStencil()
>>> but not much else I can think of;
>>>
>>>
>>> On Feb 12, 2009, at 11:44 AM, (Rebecca) Xuefei YUAN wrote:
>>>
>>>> Hi,
>>>>
>>>> I use the following set of codes to create the jacobian matrix,    
>>>>  however, the dimensions of jacobian becomes 3 (dim=3) although I  
>>>>    use DACreate2d to create this da. I wanna know where is wrong?
>>>>
>>>> ierr = DMMGCreate(comm, 1, &appCtx, &dmmg);CHKERRQ(ierr);
>>>> ierr = DACreate2d(comm,DA_XPERIODIC,DA_STENCIL_STAR, -5, -5,     
>>>> PETSC_DECIDE, PETSC_DECIDE, 4, 2, 0, 0, &da);CHKERRQ(ierr);
>>>> ierr = DMMGSetDM(dmmg, (DM)da);CHKERRQ(ierr);
>>>> ierr = DAGetMatrix(DMMGGetDA(dmmg), MATAIJ, &jacobian);CHKERRQ(ierr);
>>>>
>>>> Thanks very much!
>>>>
>>>> Rebecca
>>
>>
>>
>> -- 
>> (Rebecca) Xuefei YUAN
>> Department of Applied Physics and Applied Mathematics
>> Columbia University
>> Tel:917-399-8032
>> www.columbia.edu/~xy2102
>
>
>
> -- 
> (Rebecca) Xuefei YUAN
> Department of Applied Physics and Applied Mathematics
> Columbia University
> Tel:917-399-8032
> www.columbia.edu/~xy2102



-- 
(Rebecca) Xuefei YUAN
Department of Applied Physics and Applied Mathematics
Columbia University
Tel:917-399-8032
www.columbia.edu/~xy2102