B.ReportMetric in Go

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ReportMetric adds "n unit" to the reported benchmark results. If the metric is per-iteration, the caller should divide by b.N, and by convention units should end in "/op". ReportMetric overrides any previously reported value for the same unit. ReportMetric panics if unit is the empty string or if unit contains any whitespace. If unit is a unit normally reported by the benchmark framework itself (such as "allocs/op"), ReportMetric will override that metric. Setting "ns/op" to 0 will suppress that built-in metric.

Go
Edit 
package main

import (
	"sort"
	"testing"
)

func main() {
	// This reports a custom benchmark metric relevant to a
	// specific algorithm (in this case, sorting).
	testing.Benchmark(func(b *testing.B) {
		var compares int64
		for i := 0; i < b.N; i++ {
			s := []int{5, 4, 3, 2, 1}
			sort.Slice(s, func(i, j int) bool {
				compares++
				return s[i] < s[j]
			})
		}
		// This metric is per-operation, so divide by b.N and
		// report it as a "/op" unit.
		b.ReportMetric(float64(compares)/float64(b.N), "compares/op")
	})
}