Hello all.
I am writing to inquire if it is possible somehow to extract directly the finite differences from the Intel MKL Helmholtz solver. I am using the solver for the Poisson equation, in order to solve for the stream function Psi(x,y,z) of a fluid. In this case I am not interested in the direct value of Psi itself, but rather the gradients of Psi. Seeing as the capability exists to use Neumann boundary conditions, and it is stated in the solver description that a five-point finite difference solver is used, than I am assuming this data may be somehow stored already within the solver during execution time.
I could possibly also use the same solver, however now solving for the gradient variables -df/dx instead of -f, but this will probably end up being exactly as expensive as calculating the finite difference gradients which I am currently doing, possibly even more so due to the more expensive calculation of the gradients on the boundary. Hence why I wonder if there is a way simply to extract directly the gradient. Perhaps I am also overseeing a simple way to use the Poisson solver directly?
Any help would be appreciated.