Benchmark map[time.Time] vs map[int64]

benchmark_time.go

package main

import (
	"testing"
	"time"
)

// Package-level variables to prevent compiler optimizations
var timeMapSum int
var int64MapSum int
var lastSeenTime time.Time

func BenchmarkMapAccessTime(b *testing.B) {
	// Prepare datasets outside of the benchmark
	timeSlice := []time.Time{}
	for n := 0; n < 100000000; n++ {
		timeSlice = append(timeSlice, time.Unix(int64(n), 0))
	}

	timeMap := map[time.Time]int{}
	b.Run("time.Time", func(b *testing.B) {
		// Writes
		for n := 0; n < b.N; n++ {
			timeStruct := timeSlice[n]
			timeMap[timeStruct] = n
		}

		// Reads
		for n := 0; n < b.N; n++ {
			timeStruct := timeSlice[n]
			lastSeenTime = timeStruct
			timeMapSum += timeMap[timeStruct]
		}
	})

	// To account for the fact that maintaining the existing interfaces may involve
	// additional calls to .UnixNano() and .Unix() we include a call to each on
	// both the write and read path to benchmark the worst case
	int64Map := map[int64]int{}
	b.Run("int64", func(b *testing.B) {
		// Writes
		for n := 0; n < b.N; n++ {
			n64 := int64(timeSlice[n].UnixNano())
			lastSeenTime = time.Unix(0, n64)
			int64Map[n64] = n
			int64MapSum += int64Map[n64]
		}

		// Reads
		for n := 0; n < b.N; n++ {
			n64 := int64(timeSlice[n].UnixNano())
			lastSeenTime = time.Unix(0, n64)
			int64MapSum += int64Map[n64]
		}
	})
}

/*
go test --bench=. --benchtime=10s --count=10 --parallel=1 --cpu=1 -benchmem benchmark_time.go
BenchmarkMapAccessTime/time.Time         	30000000	      1095 ns/op	     164 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       482 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       477 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       476 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       480 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       480 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       476 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       476 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       473 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/time.Time         	30000000	       472 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       505 ns/op	      57 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       361 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       357 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       357 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       356 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       352 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       355 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       355 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       353 ns/op	       0 B/op	       0 allocs/op
BenchmarkMapAccessTime/int64             	50000000	       352 ns/op	       0 B/op	       0 allocs/op
PASS
ok  	command-line-arguments	494.040s
*/