Hello, I am trying to understand the FE Tabulation data obtained from e.g . PetscFEComputeTabulation. Using a 2D mesh with a single triangle, first order, with vertices (0,0), (0,1), (1,0) (see msh file attached), and a single quadrature point at (1/3, 1/3), one gets Nb = 6, Nc = 2, Nq = 1, and the arrays for the basis and first derivatives are of sizes [Nq x Nb x Nc] = 12 and[Nq x Nb x Nc x dim] = 24, respectively
The values of these two arrays are: basis (T->T[0]) [-1/3, 0, 0, -1/3, 2/3, 0, 0, 2/3, 2/3, 0, 0, 2/3] deriv (T->T[1]) [-1/2, -1/2, 0, 0, 0, 0, -1/2, -1/2, 1/2, 0, 0, 0, 0, 0, 1/2, 0, 0, 1/2, 0, 0, 0, 0, 0, 1/2] How does one get these values? I can't quite find a way to relate them to evaluating the basis functions of a P1 triangle in the given quadrature point. Thanks, Noam
triang01.msh
Description: Mesh model
