This method implements a linear interpolation from a lookup table.
This method uses a medium amount of memory to store d*(2*m+1)*M real numbers and requires at most
2(2m + 1)d extra multiplications for each node.
This is the default option.
Is the fastest method but requires a large amount of memory as it requires to store (2*m+1)^d*M
real numbers. No extra operations are needed during matrix vector multiplication.
(Experimental) When set to yes, for finite systems Octopus will map boundary points for finite-differences operators to a few memory locations. This increases performance, however it is experimental and has not been thoroughly tested.