Merge 47e892e into 879073f

utils.go

@@ -7,6 +7,10 @@ import (
 	"sync"
 )
 
+// MaxProcs limits the number of parallel processing subroutines to the set value.
+// A value <= 0 is ignored.
+var MaxProcs = 0
+
 // parallel processes the data in separate goroutines.
 func parallel(start, stop int, fn func(<-chan int)) {
 	count := stop - start
@@ -15,6 +19,9 @@ func parallel(start, stop int, fn func(<-chan int)) {
 	}
 
 	procs := runtime.GOMAXPROCS(0)
+	if procs > MaxProcs && MaxProcs > 0 {
+		procs = MaxProcs
+	}
 	if procs > count {
 		procs = count
 	}

utils_test.go

@@ -49,6 +49,33 @@ func testParallelN(n, procs int) bool {
 	return true
 }
 
+func TestParallelMaxProcs(t *testing.T) {
+	for _, n := range []int{0, 1, 10, 100, 1000} {
+		for _, p := range []int{1, 2, 4, 8, 16, 100} {
+			if !testParallelMaxProcsN(n, p) {
+				t.Fatalf("test [parallel %d %d] failed", n, p)
+			}
+		}
+	}
+}
+
+func testParallelMaxProcsN(n, procs int) bool {
+	data := make([]bool, n)
+	MaxProcs = procs
+	parallel(0, n, func(is <-chan int) {
+		for i := range is {
+			data[i] = true
+		}
+	})
+
+	for i := 0; i < n; i++ {
+		if !data[i] {
+			return false
+		}
+	}
+	return true
+}
+
 func TestClamp(t *testing.T) {
 	testCases := []struct {
 		f float64