PetscFECreateLagrange(comm, dim, 1, simplex, 1, PETSC_DETERMINE, &fe);
The default may be qorder = 0. Replace PETSC_DETERMINE with 1, 2, etc, and see. Thanks, Mark On Fri, Sep 8, 2023 at 6:26 PM David Andrs <[email protected]> wrote: > 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 > > -- > > >
