package lockfree

import (
	"runtime"
	"sync"
	"testing"
)

type foo struct {
	x, y, z int64
}
type foo64Start struct {
	_       [64]byte
	x, y, z int64
}
type foo64StartEnd struct {
	_       [64]byte
	x, y, z int64
	_       [64]byte
}
type foo128Start struct {
	_       [128]byte
	x, y, z int64
}
type foo128StartEnd struct {
	_       [128]byte
	x, y, z int64
	_       [128]byte
}
type foo64StartEndAligned struct {
	_       [64]byte
	x, y, z int64
	_       [64 - 24]byte
}
type foo128StartEndAligned struct {
	_       [128]byte
	x, y, z int64
	_       [128 - 24]byte
}

const iter = (1 << 16)

func BenchmarkFalseSharing(b *testing.B) {
	var wg sync.WaitGroup
	b.Run("NoPad", func(b *testing.B) {
		arr := make([]foo, runtime.GOMAXPROCS(0))
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arr {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[i].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
	b.Run("Pad64Start", func(b *testing.B) {
		arr := make([]foo64Start, runtime.GOMAXPROCS(0))
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arr {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[i].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
	b.Run("Pad64StartEnd", func(b *testing.B) {
		arr := make([]foo64StartEnd, runtime.GOMAXPROCS(0))
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arr {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[i].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
	b.Run("Pad128Start", func(b *testing.B) {
		arr := make([]foo128Start, runtime.GOMAXPROCS(0))
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arr {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[i].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
	b.Run("Pad128StartEnd", func(b *testing.B) {
		arr := make([]foo128StartEnd, runtime.GOMAXPROCS(0))
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arr {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[i].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
	b.Run("Pad64StartEndAligned", func(b *testing.B) {
		arr := make([]foo64StartEndAligned, runtime.GOMAXPROCS(0))
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arr {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[i].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
	b.Run("Pad128StartEndAligned", func(b *testing.B) {
		arr := make([]foo128StartEndAligned, runtime.GOMAXPROCS(0))
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arr {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[i].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
}
func BenchmarkTrueSharing(b *testing.B) {
	var wg sync.WaitGroup
	b.Run("<64", func(b *testing.B) {
		arr := make([]foo, runtime.GOMAXPROCS(0)*iter)
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arrChan {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[(i*iter)+j].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
	b.Run(">64", func(b *testing.B) {
		arr := make([]foo64Start, runtime.GOMAXPROCS(0)*iter)
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arrChan {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[(i*iter)+j].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
	b.Run(">128", func(b *testing.B) {
		arr := make([]foo128Start, runtime.GOMAXPROCS(0)*iter)
		arrChan := make([]chan struct{}, runtime.GOMAXPROCS(0))
		for i := range arrChan {
			arrChan[i] = make(chan struct{})
		}
		for i := range arrChan {
			go func(i int) {
				for range arrChan[i] {
					for j := 0; j < iter; j++ {
						arr[(i*iter)+j].x++
					}
					wg.Done()
				}
			}(i)
		}
		b.ResetTimer()
		for i := 0; i < b.N; i++ {
			wg.Add(runtime.GOMAXPROCS(0))
			for j := range arrChan {
				arrChan[j] <- struct{}{}
			}
			wg.Wait()
		}
		b.StopTimer()
		for i := range arrChan {
			close(arrChan[i])
		}
	})
}