Concurrently modify same atomic in stress tests (#33)

Currently, the stress tests start multiple goroutines, but they all have
their own local atomic, so they are not concurrently modifying the same
values. Return a function which can be run concurrently to modify the
same atomic.

stress_test.go

@@ -31,7 +31,7 @@ const (
 	_iterations  = 1000
 )
 
-var _stressTests = map[string]func(){
+var _stressTests = map[string]func() func(){
 	"i32":    stressInt32,
 	"i64":    stressInt64,
 	"u32":    stressUint32,
@@ -42,13 +42,14 @@ var _stressTests = map[string]func(){
 }
 
 func TestStress(t *testing.T) {
-	for name, f := range _stressTests {
+	for name, ff := range _stressTests {
 		t.Run(name, func(t *testing.T) {
 			defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(_parallelism))
 
 			start := make(chan struct{})
 			var wg sync.WaitGroup
 			wg.Add(_parallelism)
+			f := ff()
 			for i := 0; i < _parallelism; i++ {
 				go func() {
 					defer wg.Done()
@@ -65,8 +66,9 @@ func TestStress(t *testing.T) {
 }
 
 func BenchmarkStress(b *testing.B) {
-	for name, f := range _stressTests {
+	for name, ff := range _stressTests {
 		b.Run(name, func(b *testing.B) {
+			f := ff()
 			for i := 0; i < b.N; i++ {
 				f()
 			}
@@ -74,8 +76,9 @@ func BenchmarkStress(b *testing.B) {
 	}
 }
 
-func stressInt32() {
+func stressInt32() func() {
 	var atom Int32
+	return func() {
 		atom.Load()
 		atom.Add(1)
 		atom.Sub(2)
@@ -85,9 +88,11 @@ func stressInt32() {
 		atom.Swap(5)
 		atom.Store(1)
 	}
+}
 
-func stressInt64() {
+func stressInt64() func() {
 	var atom Int64
+	return func() {
 		atom.Load()
 		atom.Add(1)
 		atom.Sub(2)
@@ -97,9 +102,11 @@ func stressInt64() {
 		atom.Swap(5)
 		atom.Store(1)
 	}
+}
 
-func stressUint32() {
+func stressUint32() func() {
 	var atom Uint32
+	return func() {
 		atom.Load()
 		atom.Add(1)
 		atom.Sub(2)
@@ -109,9 +116,11 @@ func stressUint32() {
 		atom.Swap(5)
 		atom.Store(1)
 	}
+}
 
-func stressUint64() {
+func stressUint64() func() {
 	var atom Uint64
+	return func() {
 		atom.Load()
 		atom.Add(1)
 		atom.Sub(2)
@@ -121,18 +130,22 @@ func stressUint64() {
 		atom.Swap(5)
 		atom.Store(1)
 	}
+}
 
-func stressFloat64() {
+func stressFloat64() func() {
 	var atom Float64
+	return func() {
 		atom.Load()
 		atom.CAS(1.0, 0.1)
 		atom.Add(1.1)
 		atom.Sub(0.2)
 		atom.Store(1.0)
 	}
+}
 
-func stressBool() {
+func stressBool() func() {
 	var atom Bool
+	return func() {
 		atom.Load()
 		atom.Store(false)
 		atom.Swap(true)
@@ -142,9 +155,11 @@ func stressBool() {
 		atom.Toggle()
 		atom.Toggle()
 	}
+}
 
-func stressString() {
+func stressString() func() {
 	var atom String
+	return func() {
 		atom.Load()
 		atom.Store("abc")
 		atom.Load()
@@ -152,3 +167,4 @@ func stressString() {
 		atom.Load()
 		atom.Store("")
 	}
+}