xyproto / swish

:white_check_mark: Optimized Swish activation function, for neural networks

Swish

An optimized Swish activation function (Ramachandran, Zoph and Le, 2017), for neural networks.

Screenshots

The graphs above were drawn using the program in cmd/graph, which uses goterm.

Benchmark Results

Using a Swish function that uses math.Exp

First run:

goos: linux
goarch: amd64
pkg: github.com/xyproto/swish
BenchmarkSwish07-8   	200000000	         8.93 ns/op
BenchmarkSwish03-8   	200000000	         8.95 ns/op
PASS
ok  	github.com/xyproto/swish	5.391s

Using the optimized Swish function that uses exp256

goos: linux
goarch: amd64
pkg: github.com/xyproto/swish
BenchmarkSwish07-8   	2000000000	         0.26 ns/op
BenchmarkSwish03-8   	2000000000	         0.26 ns/op
PASS
ok  	github.com/xyproto/swish	1.108s

The optimized Swish function is 34x faster than the one that uses math.Exp, and quite a bit faster than my (apparently bad) attempt at a hand-written assembly version.

The average error (difference in output value) between the optimized and non-optimized version is +-0.0013 and the maximum error is +-0.0024. This is for x in the range [5,3]. See the program in cmd/precision for how this was calculated.

0.00015
0.00001
goos: linux
goarch: amd64
pkg: github.com/xyproto/swish
BenchmarkSwishAssembly07-8      500000000                3.63 ns/op
BenchmarkSwishAssembly03-8      500000000                3.65 ns/op
BenchmarkSwish07-8              2000000000               0.30 ns/op
BenchmarkSwish03-8              2000000000               0.26 ns/op
BenchmarkSwishPrecise07-8       200000000                9.07 ns/op
BenchmarkSwishPrecise03-8       200000000                9.25 ns/op
PASS
ok      github.com/xyproto/swish        11.100s

I have no idea why the assembly version is so slow, but 0.26 ns/op isn't bad for a non-hand-optimized version.

General info

• Version: 1.3.0
• License: MIT
• Author: Alexander F. Rødseth <[e-mail]>