Hi all! I am trying to use DMPlexComputeIntegralFEM to compute an integral $\int_\Omega u d\Omega$. My domain is a square (-1, 1)^2 (2x2 QUAD4 elements), I add first order Lagrange FE field on it, set the solution vector (computed by a previous simulation).
The value I am seeing computed by PETSc is -4, but the hand-calculated value of this integral is -4.6. I also checked this in paraview using the ‘Integrate Variables’ filter and it also returns -4.6 (this was to double check that my hand-calculated value is correct). So, I must be missing something obvious in my code. Attached is the minimal PETSc code to show what I am doing. This is against PETSc 3.19.4. Thanks in advance for your help, David --
main.cpp
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