[petsc-users] How to debug problem with MatSetValues

[Thomas Witkowski]

Hi,

I've some trouble with matrix values that are set by MatSetValues, but 
are missing in the final matrix. I can reduce the problem to a 75x75 
matrix that is created on four processors. I create it quite simple with:

MatCreateMPIAIJ(PETSC_COMM_WORLD, 12, 12, 75, 75, petscMatrix) on p0
MatCreateMPIAIJ(PETSC_COMM_WORLD, 18, 18, 75, 75, petscMatrix) on p1
MatCreateMPIAIJ(PETSC_COMM_WORLD, 18, 18, 75, 75, petscMatrix) on p2
MatCreateMPIAIJ(PETSC_COMM_WORLD, 27, 27, 75, 75, petscMatrix) on p3

On all processors, the values are set with the following command:

MatSetValues(petscMatrix, 1, &rowIndex, cols.size(), &(cols[0]), 
&(values[0]), ADD_VALUES);

where rowIndex is an integer, cols is of type std::vector<int> and 
values if of type std::vector<double>. Before MatSetValues is called, I 
run over the arrays and print all the entries that are added to the 
matrix. Finally,

MatAssemblyBegin(petscMatrix, MAT_FINAL_ASSEMBLY);
MatAssemblyEnd(petscMatrix, MAT_FINAL_ASSEMBLY);

are called. To check the matrix, I use the option -mat_view_matlab. 
Okay, now some of the entries are missing and I've absolute no idea what 
I did wrong (i.e. entry row 48-col 69, which is only once by rank 3).  
What is the best way to debug the problem? I use petsc 3.0.0p11, which 
is compiled in debug mode. My code is also compiled in debug mode and 
valgrind does not report any errors. Thanks for any suggestions.

Thomas