Arithmetic logic unit, data processing system, method and module
An arithmetic logic unit, comprising an addition unit for determining a sum of a first input and a second input; and a logarithmic addition unit for determining an output using the sum and a third input. The output is a multiply-accumulate output represented in a logarithmic domain when the first, second and third inputs are represented in the logarithmic domain.
1. An arithmetic logic unit for generating an output in a logarithmic domain, comprising:
an addition unit for determining a sum of a first logarithmic input and a second logarithmic input; and
a logarithmic addition unit for determining the output using the sum and a third logarithmic input, the logarithmic addition unit comprising:
a maximum detection unit, for determining a maximum value between the sum and the third logarithmic input;
a difference unit, for determining a difference between the sum and the third logarithmic input;
a fractional separation unit for determining an integer portion and a fractional portion of the difference,
an inversion unit for determining an inverse of the fractional portion;
a shifting unit for shifting the inverse by the integer portion to produce a shifted value; and
an addition unit for determining the output, wherein the output is a sum of the shifted value and the maximum value.
2. The arithmetic logic unit of claim 1 , comprising a logarithmic conversion unit, for converting data from a linear domain into the logarithmic domain to generate at least one of the first logarithmic input and second logarithmic input.
3. The arithmetic logic unit of claim 1 , comprising one or more registers arranged to receive the output, the one or more registers comprising a plurality of single-bit storage devices.
4. The arithmetic logic unit of claim 3 , wherein the third logarithmic input is derived from the one or more registers.
5. The arithmetic logic unit of claim 1 , the fractional separation unit comprises logic elements determining the integer portion and the fractional portion of the difference represented in the logarithmic domain.
6. A neural network accelerator comprising the arithmetic logic unit of claim 1 .
7. The arithmetic logic unit of claim 1 , wherein the difference unit of the logarithmic addition unit comprises a modulus unit for determining an absolute value of the difference.
8. The arithmetic logic unit of claim 1 , wherein the fractional separation unit of the logarithmic addition unit comprises a rounding module for rounding the difference, and a second subtraction unit, for determining a second difference between the first difference and the rounded difference.