package cachebenches

import (
    "math/rand"
    "runtime"
    "sort"
    "sync/atomic"
    "testing"
)

// false sharing benchmark ----------------------------------------------------

type countersUnpadded struct {
    values [8]uint64
}

type paddedCounter struct {
    value uint64
    _     [56]byte
}

type countersPadded struct {
    values [8]paddedCounter
}

func BenchmarkFalseSharing(b *testing.B) {
    runtime.GOMAXPROCS(runtime.NumCPU())

    b.Run("with_false_sharing", func(b *testing.B) {
        var c countersUnpadded
        var goroutineID uint64

        b.ResetTimer()
        b.RunParallel(func(pb *testing.PB) {
            id := atomic.AddUint64(&goroutineID, 1) - 1
            target := &c.values[id%uint64(len(c.values))]
            for pb.Next() {
                atomic.AddUint64(target, 1)
            }
        })
    })

    b.Run("with_padding", func(b *testing.B) {
        var c countersPadded
        var goroutineID uint64

        b.ResetTimer()
        b.RunParallel(func(pb *testing.PB) {
            id := atomic.AddUint64(&goroutineID, 1) - 1
            target := &c.values[id%uint64(len(c.values))].value
            for pb.Next() {
                atomic.AddUint64(target, 1)
            }
        })
    })
}