[petsc-users] Confusion about MatSetValuesStencil batching over x–dimension with DMDA

[malaboeuf at cines.fr]

Hi all, 

First, I have to apologize for I lack some experience on this subject, I have tried looking around to solve my issue without much success. 

I am assembling a 3D Laplacian matrix on a DMDA using MatSetValuesStencil. The following code, which inserts one row at a time, works as expected: 

for (PetscInt iz = info.zs; iz < info.zs + info.zm; ++iz) { 
for (PetscInt iy = info.ys; iy < info.ys + info.ym; ++iy) { 
for (PetscInt ix = info.xs; ix < info.xs + info.xm; ++ix) { 
const std::array<MatStencil, 1> rows{MatStencil{iz, iy, ix, 0}}; 
const std::array<MatStencil, 7> cols{{ 
{iz, iy, ix, 0}, 
{iz, iy, ix - 1, 0}, 
{iz, iy, ix + 1, 0}, 
{iz, iy - 1, ix, 0}, 
{iz, iy + 1, ix, 0}, 
{iz - 1, iy, ix, 0}, 
{iz + 1, iy, ix, 0} 
}}; 

CHKERRQ(MatSetValuesStencil(matrix_A, 
rows.size(), rows.data(), 
cols.size(), cols.data(), 
laplacian.data(), INSERT_VALUES)); 
} 
} 
} 

How would you batch the whole x dimension as a single MatSetValuesStencil call ? 

Each time I try, I endup getting errors such as: 
Inserting a new nonzero at global row/column (..., ...) into matrix 


Regards, 
-- 
Etienne Malaboeuf 
Ingénieur de recherche HPC, Département Calcul Intensif (DCI) 

Centre Informatique National de l'Enseignement Supérieur (CINES) 
950 rue de Saint Priest, 34097 Montpellier 
tel : (334) 67 14 14 02 
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