A Prescale-Lookup-Postscale Additive Procedure for Obtaining a Single Precision Ulp Accurate Reciprocal

Abstract

We investigate the utilization of additive prescaling for reducing the input range for determining a divisor reciprocal approximation. In particular, we demonstrate that a single precision (24-bit) ulp accurate monotonic approximate reciprocal operation can be obtained employing three back-to-back three term additions and bipartite table lookup with total table size less than 6 Kbytes.