Golang benchmarks
Golang benchmarks Basics Benchmarks are used for performance testing. Functions should import the testing package and define functions that start with Benchmark. The parameter type is testing.B, and the target function is called repeatedly inside the benchmark loop.
➜ go test -bench=. -run=none goos: darwin goarch: amd64 pkg: pkg06 cpu: Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz BenchmarkFib-12 250 4682682 ns/op PASS ok pkg06 1.875s ➜ go test -bench=. -benchmem -run=none goos: darwin goarch: amd64 pkg: pkg06 cpu: Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz BenchmarkFib-12 249 4686452 ns/op 0 B/op 0 allocs/op PASS ok pkg06 1.854s How bench works The benchmark function keeps running until b.N is no longer valid; it is the number of iterations. b.N starts at 1. If the benchmark completes within 1 second (default), b.N increases and the benchmark runs again. b.N increases in the sequence 1,2,5,10,20,50,... and the benchmark reruns. The result above means it ran 250 times in 1 second, with each run taking 4682682 ns. The -12 suffix relates to GOMAXPROCS. The default value is the number of CPUs visible to the Go process at startup. You can change it with -cpu, and pass multiple values to run multiple benchmarks. Run with multiple CPU counts ➜ go test -bench=. -cpu=1,2,4 -benchmem -run=none goos: darwin goarch: amd64 pkg: pkg06 cpu: Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz BenchmarkFib 244 4694667 ns/op 0 B/op 0 allocs/op BenchmarkFib-2 255 4721201 ns/op 0 B/op 0 allocs/op BenchmarkFib-4 256 4756392 ns/op 0 B/op 0 allocs/op PASS ok pkg06 5.826s Run benchmarks multiple times with count Due to CPU throttling, memory locality, background work, GC activity, etc., a single run may be noisy. It is common to run benchmarks multiple times.
