fix: cross platform float compatibility

loadtester/variance.go

@@ -47,13 +47,17 @@ func (wv *welfordVariance) Variance(count int) float64 {
 //
 // Note that if you copy this function it really should panic if the input is negative. Variance cannot be negative!
 func varianceFloatString(f float64) string {
+	// round first thing because it can cause an overflow on various CPU architectures
+	f = math.Round(f)
+
 	if math.IsNaN(f) {
 		return ""
 	}
 
 	v := int64(math.MaxInt64)
 	if !math.IsInf(f, 1) {
-		v = int64(math.Round(f))
+		// converting to int64 requires a "& math.MaxInt64" because it can cause an overflow on various CPU architectures
+		v = int64(f) & math.MaxInt64
 	}
 
 	return strconv.FormatInt(v, 10)

loadtester/variance_test.go

@@ -20,7 +20,7 @@ func Test_varianceFloatString(t *testing.T) {
 	}
 	{
 		// garbage in - garbage out case
-		exp := "-9223372036854775808"
+		exp := "0"
 		if v := varianceFloatString(math.Inf(-1)); v != exp {
 			t.Fatalf("expected %s string, got %s", exp, v)
 		}
@@ -33,7 +33,7 @@ func Test_varianceFloatString(t *testing.T) {
 	}
 	{
 		// garbage in - garbage out case
-		exp := "-1"
+		exp := "9223372036854775807"
 		if v := varianceFloatString(-1.0); v != exp {
 			t.Fatalf("expected %s string, got %s", exp, v)
 		}