IF AN EXPERT SAYS IT CAN'T BE DONE GET ANOTHER EXPERT.
While working on the Gomobiledetect package I have been facing some interesting performance issues such as caching the compiled regex rules and changing the maps to slices(expandable arrays on runtime) or arrays(fixed size) - depends on the situation.
Today I want to talk about the performance improvement I have faced while working on gomobiledetect.
Before getting into the package's improvements, lets start with a basic example. I have written a small package which uses 3 different structures:
The benchmarks include:
$ map-vs-slice-vs-array $ go test -bench=. testing: warning: no tests to run PASS BenchmarkDeferRecoverPanicMap 10000 215850 ns/op BenchmarkDeferRecoverPanicSliceExpandable 100000 28785 ns/op BenchmarkDeferRecoverPanicSliceFixedSize 200000 14172 ns/op BenchmarkDeferRecoverPanicArray 200000 8329 ns/op BenchmarkRunMap 10000 215273 ns/op BenchmarkRunSliceExpandable 100000 27926 ns/op BenchmarkRunSliceFixedSize 200000 13603 ns/op BenchmarkRunArray 500000 5959 ns/op BenchmarkSearchMap 10000 254402 ns/op BenchmarkSearchSliceExpandable 100000 28852 ns/op BenchmarkSearchSliceFixedSize 100000 14869 ns/op BenchmarkSearchArray 200000 8632 ns/op BenchmarkDeleteMap 10000 260431 ns/op BenchmarkDeleteSlicePreservingOrder 500000 7045 ns/op BenchmarkDeleteSliceWithoutPreservingOrder 500000 5876 ns/op ok Shaked/map-vs-slice-vs-array 39.698s
Basically the difference between the simple example and this example is only the types that I have used, e.g:
complex $ go test -bench=. testing: warning: no tests to run PASS BenchmarkDeferRecoverPanicMap 5000 302902 ns/op BenchmarkDeferRecoverPanicSliceExpandable 10000 114866 ns/op BenchmarkDeferRecoverPanicSliceFixedSize 20000 91200 ns/op BenchmarkDeferRecoverPanicArray 20000 90487 ns/op BenchmarkRunMap 10000 297342 ns/op BenchmarkRunSliceExpandable 10000 110090 ns/op BenchmarkRunSliceFixedSize 20000 89525 ns/op BenchmarkRunArray 20000 96333 ns/op BenchmarkSearchMap 5000 335909 ns/op BenchmarkSearchSliceExpandable 10000 113070 ns/op BenchmarkSearchSliceFixedSize 20000 91075 ns/op BenchmarkSearchArray 20000 89402 ns/op BenchmarkDeleteMap 5000 348145 ns/op BenchmarkDeleteSlicePreservingOrder 200000 7810 ns/op BenchmarkDeleteSliceWithoutPreservingOrder 500000 7163 ns/op ok Shaked/map-vs-slice-vs-array/complex 33.417s
I have made a lot of changes in the package which can be seen here
The results were amazing. The old version including maps showed:
BenchmarkIsMobile 2000 1001884 ns/op ok github.com/Shaked/gomobiledetect 7.091s
While the current version showed:
BenchmarkIsMobile 100000 19278 ns/op ok github.com/Shaked/gomobiledetect 7.448s
At the moment I have decided to continue supporting backwards which means that I am still using a map that maps between the string and the integer value of the keys.
I think that its clear that one should aim to use proper arrays or slices but then as we know that maps are needed a good question would be: when?