On 18/07/16 15:49, Lulu Liu wrote:

Hi,

I add the following lines in the example /petsc/src/snes/examples/tutorials/ex19. When I run this example using different numbers of processors, n always equals to 1. However, according to the manual, n is the number of subproblems in the domain decomposition. I feel confused why n does not return the number of processors, could you explain it? Thanks!

PetscInt n; DM *subdms; ierr =DMCreateDomainDecomposition(da,&n,NULL,NULL,NULL,&subdms);CHKERRQ(ierr); PetscPrintf(PETSC_COMM_WORLD,"### n==%d\n", n);

You need to do -da_local_subdomains nsubdomain_per_process or else call DMDASetNumLocalSubdomains Cheers, Lawrence