公开(公告)号：US20240296010A1

公开(公告)日：2024-09-05

申请号：US18591349

申请日：2024-02-29

Applicant: Graphcore Limited

Inventor： Thomas BROWN

IPC: G06F7/499 ,  G06F7/523 ,  G06F7/556

CPC classification number: G06F7/49915 ,  G06F7/523 ,  G06F7/556

Abstract: A processing unit is provided with circuitry enabling execution quick evaluation of an exponential function. A multiplier circuit is used to multiply the input operand by log2(e), such that a result for the exponential function may be determined by evaluating 2i+f, where i is an integer part of a fixed-point number and f is a fractional part of the fixed-point number. A lookup table is used for providing an estimate for 2f based on the l MSBs of f. The lookup entries are provided according to a function such that the estimates for 2f are provided without bias towards either zero or infinity in the result. In other words, the maximum multiplicative error for each entry of the lookup table is the same in both negative and positive directions. In this way, statistical errors in the evaluation of a large number of exponential functions may be avoided.