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<p>Ah I get it, thanks!<br>
</p>
<div class="moz-cite-prefix">On 8/10/20 5:40 PM, Matthew Knepley
wrote:<br>
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<div dir="ltr">On Mon, Aug 10, 2020 at 6:26 PM Nidish <<a
href="mailto:nb25@rice.edu" moz-do-not-send="true">nb25@rice.edu</a>>
wrote:<br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">Ah I get it now,
MatSetBlocked has to be set node-wise. I tried this and <br>
it works, thank you.<br>
<br>
The other question I had was why are the arguments for
MatSetValues() <br>
and MatSetValuesBlocked() set to const PetscInt* and const
PetscScalar* <br>
instead of just PetscInt* and PetscScalar* ? I have the
typecast there <br>
so my flycheck doesn't keep throwing me warnings on emacs ;)<br>
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<div>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.</div>
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<div> Thanks,</div>
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<div> Matt</div>
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Thank You,<br>
Nidish<br>
<br>
On 8/10/20 5:16 PM, Jed Brown wrote:<br>
> Nidish <<a href="mailto:nb25@rice.edu"
target="_blank" moz-do-not-send="true">nb25@rice.edu</a>>
writes:<br>
><br>
>> It's a 1D model with displacements and rotations as
DoFs at each node.<br>
>><br>
>> I couldn't find much in the manual on
MatSetBlockSize - could you<br>
>> provide some more information on its use?<br>
>><br>
>> I thought since I've setup the system using
DMDACreate1d (I've given<br>
>> 2dofs per node and a stencil width of 1 there), the
matrix object should<br>
>> have the nonzero elements preallocated. Here's the
call to DMDACreate1d:<br>
>><br>
>> DMDACreate1d(PETSC_COMM_WORLD,
DM_BOUNDARY_NONE, N, 2, 1, NULL, &mshdm);<br>
> Ah, that will set the block size, but then it'll expect
elstiff to be an 8x8 matrix where you've only passed 4x4.<br>
><br>
> idx[0] = 2*e; idx[1] = 2*e+1; idx[2] = 2*e+2;
idx[3] = 2*e+3;<br>
><br>
> MatSetValuesBlocked(jac, 4, (const PetscInt*)idx,
4, (const PetscInt*)idx,<br>
> (const PetscScalar*)elstiff,
ADD_VALUES);<br>
><br>
> You don't need the casts in either case, BTW. You
probably want something like this.<br>
><br>
> idx[0] = e; idx[1] = e + 1;<br>
><br>
> MatSetValuesBlocked(jac, 2, idx, 2, idx, elstiff,
ADD_VALUES);<br>
><br>
> Also, it might be more convenient to call
MatSetValuesBlockedStencil(), especially if you move to a
multi-dimensional problem at some point.<br>
-- <br>
Nidish<br>
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-- <br>
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<div>What most experimenters take for granted before
they begin their experiments is infinitely more
interesting than any results to which their
experiments lead.<br>
-- Norbert Wiener</div>
<div><br>
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<div><a href="http://www.cse.buffalo.edu/~knepley/"
target="_blank" moz-do-not-send="true">https://www.cse.buffalo.edu/~knepley/</a><br>
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<div class="moz-signature">-- <br>
Nidish</div>
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