This benchmark measures the performance of branching with a switch calling a function vs using a map of functions. For example:
// Given f is map[int]func()
f[n](i)vs.
switch n {
case 0:
a()
case 1:
b()
case 2:
c()
case 3:
d()
}Cases with 4, 8, 16, 32, 64, 128, 256, and 512 branches are included in this benchmark.
The switch statement may benefit from inlining simple functions. This benchmark tests the difference between functions that can be inlined and those that cannot. The Go compiler does not inline functions that can panic. The non-inlinable functions include an unreachable panic to block inlining.
Some tests sequentially follow branch 0, 1, 2, etc. Others visit branches in a random order.
- Compute destination benchmarks use the benchmark loop's index as the branch discriminator. This loops through branches in a predictable manner (e.g.
i % 4for a case with 4 branches). - Lookup destination benchmarks use the loop's index to look up the branch to take in pre-computed slice. (e.g.
ascInputs[i%len(ascInputs)] % 4for a case with 4 branches).
go get github.com/jackc/go_map_vs_switch
cd $GOPATH/src/github.com/jackc/go_map_vs_switch
go test -test.bench=.
These benchmarks contain a great deal of repetitive code. The Ruby tools rake and erb are used to automate the generation of these benchmarks. You do not need Ruby to run the benchmarks. However, if you wish to make changes you will need a Ruby install. Simply change the *.erb files and run rake.
The following results were produced from a Intel i7-4790K running go1.5.1 linux/amd64 on Ubuntu 14.04.
BenchmarkPredictableComputedSwitchInlineFunc4-8 2000000000 1.99 ns/op
BenchmarkPredictableComputedMapInlineFunc4-8 1000000000 2.38 ns/op
BenchmarkPredictableLookupSwitchInlineFunc4-8 200000000 8.16 ns/op
BenchmarkPredictableLookupMapInlineFunc4-8 100000000 10.6 ns/op
BenchmarkUnpredictableLookupSwitchInlineFunc4-8 100000000 14.2 ns/op
BenchmarkUnpredictableLookupMapInlineFunc4-8 100000000 19.0 ns/op
BenchmarkPredictableComputedSwitchNoInlineFunc4-8 500000000 3.46 ns/op
BenchmarkPredictableComputedMapNoInlineFunc4-8 1000000000 2.69 ns/op
BenchmarkPredictableLookupSwitchNoInlineFunc4-8 100000000 11.0 ns/op
BenchmarkPredictableLookupMapNoInlineFunc4-8 100000000 11.1 ns/op
BenchmarkUnpredictableLookupSwitchNoInlineFunc4-8 100000000 17.6 ns/op
BenchmarkUnpredictableLookupMapNoInlineFunc4-8 100000000 19.7 ns/op
BenchmarkPredictableComputedSwitchInlineFunc8-8 1000000000 2.33 ns/op
BenchmarkPredictableComputedMapInlineFunc8-8 1000000000 2.39 ns/op
BenchmarkPredictableLookupSwitchInlineFunc8-8 200000000 9.70 ns/op
BenchmarkPredictableLookupMapInlineFunc8-8 100000000 10.5 ns/op
BenchmarkUnpredictableLookupSwitchInlineFunc8-8 100000000 16.5 ns/op
BenchmarkUnpredictableLookupMapInlineFunc8-8 100000000 20.4 ns/op
BenchmarkPredictableComputedSwitchNoInlineFunc8-8 500000000 3.76 ns/op
BenchmarkPredictableComputedMapNoInlineFunc8-8 1000000000 2.75 ns/op
BenchmarkPredictableLookupSwitchNoInlineFunc8-8 100000000 11.6 ns/op
BenchmarkPredictableLookupMapNoInlineFunc8-8 100000000 10.9 ns/op
BenchmarkUnpredictableLookupSwitchNoInlineFunc8-8 100000000 20.0 ns/op
BenchmarkUnpredictableLookupMapNoInlineFunc8-8 100000000 21.1 ns/op
BenchmarkPredictableComputedSwitchInlineFunc16-8 1000000000 2.60 ns/op
BenchmarkPredictableComputedMapInlineFunc16-8 1000000000 2.52 ns/op
BenchmarkPredictableLookupSwitchInlineFunc16-8 200000000 8.96 ns/op
BenchmarkPredictableLookupMapInlineFunc16-8 100000000 10.6 ns/op
BenchmarkUnpredictableLookupSwitchInlineFunc16-8 100000000 19.3 ns/op
BenchmarkUnpredictableLookupMapInlineFunc16-8 100000000 21.1 ns/op
BenchmarkPredictableComputedSwitchNoInlineFunc16-8 300000000 4.14 ns/op
BenchmarkPredictableComputedMapNoInlineFunc16-8 1000000000 2.69 ns/op
BenchmarkPredictableLookupSwitchNoInlineFunc16-8 100000000 11.7 ns/op
BenchmarkPredictableLookupMapNoInlineFunc16-8 100000000 10.9 ns/op
BenchmarkUnpredictableLookupSwitchNoInlineFunc16-8 50000000 23.9 ns/op
BenchmarkUnpredictableLookupMapNoInlineFunc16-8 100000000 21.9 ns/op
BenchmarkPredictableComputedSwitchInlineFunc32-8 1000000000 2.75 ns/op
BenchmarkPredictableComputedMapInlineFunc32-8 1000000000 2.39 ns/op
BenchmarkPredictableLookupSwitchInlineFunc32-8 200000000 9.10 ns/op
BenchmarkPredictableLookupMapInlineFunc32-8 100000000 10.6 ns/op
BenchmarkUnpredictableLookupSwitchInlineFunc32-8 50000000 22.8 ns/op
BenchmarkUnpredictableLookupMapInlineFunc32-8 100000000 21.7 ns/op
BenchmarkPredictableComputedSwitchNoInlineFunc32-8 300000000 4.24 ns/op
BenchmarkPredictableComputedMapNoInlineFunc32-8 1000000000 2.75 ns/op
BenchmarkPredictableLookupSwitchNoInlineFunc32-8 100000000 11.9 ns/op
BenchmarkPredictableLookupMapNoInlineFunc32-8 100000000 11.0 ns/op
BenchmarkUnpredictableLookupSwitchNoInlineFunc32-8 50000000 27.5 ns/op
BenchmarkUnpredictableLookupMapNoInlineFunc32-8 50000000 22.0 ns/op
BenchmarkPredictableComputedSwitchInlineFunc64-8 500000000 3.16 ns/op
BenchmarkPredictableComputedMapInlineFunc64-8 1000000000 2.38 ns/op
BenchmarkPredictableLookupSwitchInlineFunc64-8 200000000 9.37 ns/op
BenchmarkPredictableLookupMapInlineFunc64-8 100000000 10.6 ns/op
BenchmarkUnpredictableLookupSwitchInlineFunc64-8 50000000 26.8 ns/op
BenchmarkUnpredictableLookupMapInlineFunc64-8 50000000 22.1 ns/op
BenchmarkPredictableComputedSwitchNoInlineFunc64-8 300000000 4.91 ns/op
BenchmarkPredictableComputedMapNoInlineFunc64-8 500000000 3.20 ns/op
BenchmarkPredictableLookupSwitchNoInlineFunc64-8 100000000 12.2 ns/op
BenchmarkPredictableLookupMapNoInlineFunc64-8 100000000 11.0 ns/op
BenchmarkUnpredictableLookupSwitchNoInlineFunc64-8 50000000 31.9 ns/op
BenchmarkUnpredictableLookupMapNoInlineFunc64-8 50000000 23.6 ns/op
BenchmarkPredictableComputedSwitchInlineFunc128-8 500000000 3.68 ns/op
BenchmarkPredictableComputedMapInlineFunc128-8 1000000000 2.60 ns/op
BenchmarkPredictableLookupSwitchInlineFunc128-8 100000000 10.2 ns/op
BenchmarkPredictableLookupMapInlineFunc128-8 100000000 10.6 ns/op
BenchmarkUnpredictableLookupSwitchInlineFunc128-8 50000000 31.0 ns/op
BenchmarkUnpredictableLookupMapInlineFunc128-8 50000000 22.4 ns/op
BenchmarkPredictableComputedSwitchNoInlineFunc128-8 300000000 5.17 ns/op
BenchmarkPredictableComputedMapNoInlineFunc128-8 500000000 3.24 ns/op
BenchmarkPredictableLookupSwitchNoInlineFunc128-8 100000000 12.5 ns/op
BenchmarkPredictableLookupMapNoInlineFunc128-8 100000000 11.0 ns/op
BenchmarkUnpredictableLookupSwitchNoInlineFunc128-8 50000000 35.5 ns/op
BenchmarkUnpredictableLookupMapNoInlineFunc128-8 50000000 23.9 ns/op
BenchmarkPredictableComputedSwitchInlineFunc256-8 300000000 4.13 ns/op
BenchmarkPredictableComputedMapInlineFunc256-8 1000000000 2.98 ns/op
BenchmarkPredictableLookupSwitchInlineFunc256-8 100000000 10.8 ns/op
BenchmarkPredictableLookupMapInlineFunc256-8 100000000 10.7 ns/op
BenchmarkUnpredictableLookupSwitchInlineFunc256-8 50000000 34.4 ns/op
BenchmarkUnpredictableLookupMapInlineFunc256-8 50000000 22.6 ns/op
BenchmarkPredictableComputedSwitchNoInlineFunc256-8 300000000 5.76 ns/op
BenchmarkPredictableComputedMapNoInlineFunc256-8 500000000 3.81 ns/op
BenchmarkPredictableLookupSwitchNoInlineFunc256-8 100000000 13.2 ns/op
BenchmarkPredictableLookupMapNoInlineFunc256-8 100000000 11.1 ns/op
BenchmarkUnpredictableLookupSwitchNoInlineFunc256-8 30000000 41.0 ns/op
BenchmarkUnpredictableLookupMapNoInlineFunc256-8 50000000 25.5 ns/op
BenchmarkPredictableComputedSwitchInlineFunc512-8 300000000 4.39 ns/op
BenchmarkPredictableComputedMapInlineFunc512-8 500000000 2.86 ns/op
BenchmarkPredictableLookupSwitchInlineFunc512-8 100000000 11.4 ns/op
BenchmarkPredictableLookupMapInlineFunc512-8 100000000 11.1 ns/op
BenchmarkUnpredictableLookupSwitchInlineFunc512-8 30000000 39.3 ns/op
BenchmarkUnpredictableLookupMapInlineFunc512-8 50000000 22.7 ns/op
BenchmarkPredictableComputedSwitchNoInlineFunc512-8 100000000 12.5 ns/op
BenchmarkPredictableComputedMapNoInlineFunc512-8 300000000 3.91 ns/op
BenchmarkPredictableLookupSwitchNoInlineFunc512-8 100000000 18.2 ns/op
BenchmarkPredictableLookupMapNoInlineFunc512-8 100000000 11.6 ns/op
BenchmarkUnpredictableLookupSwitchNoInlineFunc512-8 30000000 46.9 ns/op
BenchmarkUnpredictableLookupMapNoInlineFunc512-8 50000000 27.2 ns/op