Direct Approximation of a Function or Its Inverse
Piecewise linear approximation (sometimes loosely referred to as “table lookup”) is readily extended to second order fits.
Piecewise linear approximation is readily extended to two dimensions.
In either case, the approximating coefficients are computed only once (before or at initialization).
This strategy is much faster than conventional methods, and does not compromise accuracy.
It does require experience with modern architectures, approximation theory and dense test procedures.
A surfeit of low-cost DRAM makes this approach feasible.