Evaluating products of nonlinear functions by indirect bipartite table lookup
David W. Matula, A. Fit-Florea, Lee D. McFearin · 2003
Many function approximation procedures can obtain enhanced accuracy by an efficient table lookup of a product z=f(x)g(y). Both x and y are represented by indices of i leading bits (typically 7<i<16) for arguments normalized to [0, 1] or [1, 2]. Direct bipartite lookup employs 1/2 bits each of x and y yielding roughly an 1/2 bit result which can lose 2 to 3 bits of accuracy when f and g are nonlinear. Indirect bipartite lookup first generates i/2 bit interval index values for f(x) and g(y) using separate j-bits-in 1/2bits-out tables for f(x) and g(y) where i/2<j