Sonums.jl

A software emulator for Sonums - the Self-Organizing NUMbers. A number format that learns from data. Sonum8 is the 8bit version, Sonum16 for 16bit computations. This number format shares many similarities with the type II unums developed by John Gustafson.

Usage

Load the emulator with using Sonums, then train the 8 or 16bit Sonums with your data (a maximum entropy approach is used)

data = randn(10_000_000)
trainSonum8(data)
trainSonum16(data)

Alternatively, you can also use a 127-element vector (8bit) or 32767-element vector (16bit) to set the representable Sonums directly. To imitate Posit8 for example you may do

using SoftPosit
posit8 = Float64.(Posit8.(UInt8.(collect(1:127))))  # creates a list of Posit8 numbers in (0,Inf)
setSonum8(posit8)
setUnderflow8(false)  # Posits don't underflow but Sonums do by default

Once either Sonum8 or Sonum16 is set up, you have to fill the lookup tables for all arithmetic operations

fillSonumTables8()    #  8bit: this is quick
fillSonumTables16()   # 16bit: this may take a few minutes

And now we can do things like

julia> a = Sonum16(1.2);
julia> b = Sonum16(0.5);
julia> a-b
Sonum16(0x420a)
julia> Float64(a-b)
0.7000189572298372
julia> Float64(sqrt(a))
1.0954481925887807

Theory

The Sonum circle follows closely the idea of the posit circle developed by John Gustafson. Instead of imposing a symmetry with respect to the multiplicative inverse, as proposed for the type II unums, Sonums only have a additive symmetry around 0. The 4bit Sonum circle is therefore

with values s₁ to s₇ to be defined. The bitpattern 0000 is reserved for 0, and 1000 for NaR (not a real). Negative numbers directly follow as the two's complement for any s₁ to s₇.

Benchmarking

Unfortunately the table lookup matrices require 5GB (1GB per table, 2GB for division) of RAM for 16bit (<1Mb for 8bit). However, arithmetic operations are reasonably fast. In order to avoid caching in the benchmarking, we perform operations over arrays

julia> using BenchmarkTools

julia> N = 100000;

julia> a = Sonum16.(randn(N));

julia> b = Sonum16.(randn(N));

julia> @btime +($a,$b);
  2.358 ms (2 allocations: 195.39 KiB)

julia> @btime -($a,$b);
  2.348 ms (2 allocations: 195.39 KiB)

julia> @btime .*($a,$b);
  1.829 ms (2 allocations: 195.39 KiB)

julia> @btime ./($a,$b);
  1.753 ms (2 allocations: 195.39 KiB)

julia> @btime sqrt.($a);
  433.788 μs (2 allocations: 195.39 KiB)

So that +,- require ca. 2.35ms/N = 23.5ns, *,/ ca 1.8ms/N = 18ns and sqrt ca. 4.3ns

Testing

Sonums are tested against the SoftPosit library: Once set up with Posits, Sonums yield bitwise-reproducible results for +,-,*,/. See here

Installation

In the package manager do

(v1.1) pkg> add https://www.github.com/milankl/Sonums.jl