Ah I get it, thanks!
On 8/10/20 5:40 PM, Matthew Knepley wrote:
On Mon, Aug 10, 2020 at 6:26 PM Nidish <[email protected]
<mailto:[email protected]>> wrote:
Ah I get it now, MatSetBlocked has to be set node-wise. I tried
this and
it works, thank you.
The other question I had was why are the arguments for MatSetValues()
and MatSetValuesBlocked() set to const PetscInt* and const
PetscScalar*
instead of just PetscInt* and PetscScalar* ? I have the typecast
there
so my flycheck doesn't keep throwing me warnings on emacs ;)
Jed is correct that this cast is implicit. The idea here is to tell
the caller that we will not change the contents of the arrays that you
pass in.
Thanks,
Matt
Thank You,
Nidish
On 8/10/20 5:16 PM, Jed Brown wrote:
> Nidish <[email protected] <mailto:[email protected]>> writes:
>
>> It's a 1D model with displacements and rotations as DoFs at
each node.
>>
>> I couldn't find much in the manual on MatSetBlockSize - could you
>> provide some more information on its use?
>>
>> I thought since I've setup the system using DMDACreate1d (I've
given
>> 2dofs per node and a stencil width of 1 there), the matrix
object should
>> have the nonzero elements preallocated. Here's the call to
DMDACreate1d:
>>
>> DMDACreate1d(PETSC_COMM_WORLD, DM_BOUNDARY_NONE, N, 2, 1,
NULL, &mshdm);
> Ah, that will set the block size, but then it'll expect elstiff
to be an 8x8 matrix where you've only passed 4x4.
>
> idx[0] = 2*e; idx[1] = 2*e+1; idx[2] = 2*e+2; idx[3] = 2*e+3;
>
> MatSetValuesBlocked(jac, 4, (const PetscInt*)idx, 4, (const
PetscInt*)idx,
> (const PetscScalar*)elstiff, ADD_VALUES);
>
> You don't need the casts in either case, BTW. You probably want
something like this.
>
> idx[0] = e; idx[1] = e + 1;
>
> MatSetValuesBlocked(jac, 2, idx, 2, idx, elstiff, ADD_VALUES);
>
> Also, it might be more convenient to call
MatSetValuesBlockedStencil(), especially if you move to a
multi-dimensional problem at some point.
--
Nidish
--
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
https://www.cse.buffalo.edu/~knepley/
<http://www.cse.buffalo.edu/~knepley/>
--
Nidish
