[petsc-users] Transpose MATMPIBAIJ matrix

[S.H.Jongsma at utwente.nl]

Hello fellow PETSc users,

 

While using PETSc I came across some conspicuous behavior regarding the
use of MatTranspose.  When I use this function with a MATSEQBAIJ matrix
it performs considerably better than when I use it with a MATMPIBAIJ
matrix. I was wondering if anyone of you noticed the same behavior and
if this is the case, what did you do about it to circumvent the
'problem'. In case no one came across this problem before, any
suggestions that can help solving this performance issue are welcome. 

 

To make my problem more clear, I will give some details on my
implementation and the test I performed to come to my conclusion. The
PETSc version I use is 3.1-p8. I transpose the matrix in place using the
following command:

 

MatTranspose(myMatrix, MAT_REUSE_MATRIX, &myMatrix);

 

The matrix I used to test the performance is square and consists of
24576 times 24576 blocks of size 5, which means that the matrix has
122880 rows (and columns, of course). The number of non-zero blocks in
the matrix is: 291830. Timing the performance gives the following
results:

 

MATSEQBAIJ:    0.320 s

MATMPIBAIJ: 1474     s (running on 1 processor) 

MATMPIBAIJ:  376     s (running on 2 processors)

 

As I said, the difference in performance is quite considerable, so any
suggestion that can help me solving this issue are greatly appreciated. 

 

Thank you in advance,

 

Kind regards,

 

 

Sietse Jongsma

 

 

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