[petsc-users] questions about dm/examples/tutorials/ex5.c

Xiangdong epscodes at gmail.com
Wed Feb 19 10:40:33 CST 2014

Hello everyone,

I am running the dm tutorial ex5. I have a few quick questions:

1) what do DMDA_ELEMENT_P1 and DMDA_ELEMENT_Q1 mean? I googled, but did not
find the answer.

2) the m and n for DMDACreate2d are used as PETSC_DECIDE. when I print
these values, it seems that m=-1 and n=-1. Can the number of processors per
dimension be negative? Does -1 corresponds to some special meaning in PETSc?

3) When I run the program with np=1, I get ne=126 and nc=3 from
DMDAGetElements(da,&ne,&nc,&e). It is not clear for me where 126 and 3 come
from. Can you explain a little bit?

Thank you.

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