Dear Firedrakers, I decided to create another set of cohomology tests, this time with Dirichlet boundary conditions, since there is a nice result relating the kernels of the operators with and without Dirichlet boundary conditions (for the maths-curious, it's Poincare duality). However, I can't get the boundary tags into Firedrake from gmsh. If I attempt to tag the boundary using "Physical Line" in gmsh (see bottom of this email for the .geo file), the line

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mesh = Mesh("annulus.msh") produces: *** ERROR *** Error message: Unsupported mixture of face/element types

Removing the physical line makes the error message go away, so there is something wrong with that line. What have I done wrong? all the best --Colin Point(1) = {0, 0, 0, 1.0}; Point(2) = {1, 0, 0, 1.0}; Point(3) = {1, 1, 0, 1.0}; Point(4) = {0, 1, 0, 1.0}; Point(5) = {0.3333333333333, 0.3333333333333, 0, 1.0}; Point(6) = {0.66666666666666, 0.3333333333333, 0, 1.0}; Point(7) = {0.66666666666666, 0.66666666666666, 0, 1.0}; Point(8) = {0.3333333333333, 0.66666666666666, 0, 1.0}; Line(1) = {1, 2}; Line(2) = {2, 3}; Line(3) = {3, 4}; Line(4) = {4, 1}; Line(5) = {5, 6}; Line(6) = {6, 7}; Line(7) = {7, 8}; Line(8) = {8, 5}; Line Loop(1) = {1, 2, 3, 4}; Line Loop(2) = {5, 6, 7, 8}; Plane Surface(1) = {1,2}; Physical Line(9) = {2, 3, 4, 1, 6, 7, 8, 5};