[Trilinos-Users] Question about FillComplete for EpetraCRS matrix

[Natarajan CS]

Mike,
    Thanks for the suggestion. This was a mistake on my side, should have
taken a closer look at the matrix! With help from a colleague we figured It
was not a memory leak but rather a bad algorithmic issue. i was inserting
values where there shouldn't have been values. i.e node 4 (in a 2*2*2
system) for example had a -1 in the first sub-diagonal and that should not
have been the case! This makes me wonder, how exactly does FillComplete
function? In essence by goofing up my stencil I would think I am only
changing the sparsity pattern, so if all Fill complete is doing is changing
the indexing, why is there a problem?

Also as an aside, the current allocation of nodes to processors seems like
dividing linearly (i.e n/p nodes to each processor), is there another way to
do this? i mean distributing nodes in a checker board pattern? i.e
nx/px,ny/py,nz/pz nodes in each direction to every processor?

Thanks again for the help, much appreciated.


On Thu, May 20, 2010 at 11:18 AM, Heroux, Michael A <maherou at sandia.gov>wrote:

>  Have you tried a memory checking tool on your code?  This looks a bit
> like a memory error.  If you can run something like valgrind (which is
> freely available for Linux systems) on your code, you might see the problem
> quickly.
>
> Mike
>
>
> On 5/19/10 5:25 PM, "Natarajan CS" <csnataraj at gmail.com> wrote:
>
> Sorry about the repost, made a quality goof up while typing, so resending
> the code snippet. The matrix also looks correct when I o/p it, so not sure
> where exactly I am messing things up!
>
> for eg for 2*2*2 grid points :
>
>    Processor    Row Index    Col Index           Value
>        0             0             1                      -1
>        0             0             2                      -1
>        0             0             4                      -1
>        0             0             0                       6
>        0             1             0                      -1
>        0             1             3                      -1
>        0             1             5                      -1
>        0             1             1                       6
>        0             2             3                      -1
>        0             2             0                      -1
>        0             2             6                      -1
>        0             2             2                       6
>        0             3             2                      -1
>        0             3             1                      -1
>        0             3             7                      -1
>        0             3             3                       6
>        1             4             5                      -1
>        1             4             2                      -1
>        1             4             6                      -1
>        1             4             0                      -1
>        1             4             4                       6
>        1             5             4                      -1
>        1             5             3                      -1
>        1             5             7                      -1
>        1             5             1                      -1
>        1             5             5                       6
>        1             6             7                      -1
>        1             6             4                      -1
>        1             6             8                      -1
>        1             6             2                      -1
>        1             6             6                       6
>        1             7             6                      -1
>        1             7             5                      -1
>        1             7             9                      -1
>        1             7             3                      -1
>        1             7             7                       6
>
> .
>
> On Wed, May 19, 2010 at 1:54 PM, Natarajan CS <csnataraj at gmail.com> wrote:
>
> Hello All,
>        I came across the following error (attached) when trying to create a
> laplacian stencil for 3D. I appreciate any help in figuring out if this is
> an algorithmic issue or a trilinos issue. The code crashes during
> FillComplete. I am only sending the relevant functions, however, if someone
> would like to reproduce the issue, I will be happy to send them the code. I
> couldn't find anything similar in the archives, so apologies if a similar
> question has been answered before. I have attached the portions of the code
> that give the bug below and the back trace, if any, from gdb. I am using the
> intel compiler with vendor blas and lapack.
>
> Cheers and thanks in advance,
>
> C.S.N
> ************************************************************
>
>
>
>
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