vlib: add an arrays.parallel module, containing parallel.run/3 and parallel.amap/3 implementations (#22090)

vlib/arrays/parallel/parallel_test.v

@@ -0,0 +1,66 @@
+import arrays.parallel
+import rand
+import time
+
+fn test_parallel_run_with_empty_arrays() {
+	parallel.run([]int{}, fn (x int) {})
+	parallel.run([]u8{}, fn (x u8) {})
+	parallel.run([]u32{}, fn (x u32) {}, workers: 1000)
+	assert true
+}
+
+fn test_parallel_amap_with_empty_arrays() {
+	assert parallel.amap([]int{}, fn (x int) u8 {
+		return 0
+	}) == []
+	assert parallel.amap([]u8{}, fn (x u8) int {
+		return 0
+	}) == []
+	assert parallel.amap([]u8{}, fn (x u8) int {
+		return 0
+	}, workers: 1000) == []
+	assert true
+}
+
+fn test_parallel_run() {
+	counters := []int{len: 10, init: index}
+	dump(counters)
+	mut res := []string{len: 10}
+	mut pres := &res
+	parallel.run(counters, fn [mut pres] (i int) {
+		delay := rand.intn(250) or { 250 }
+		time.sleep(delay * time.millisecond)
+		unsafe {
+			pres[i] = 'task ${i}, delay=${delay}ms'
+		}
+		assert true
+	})
+	dump(res)
+	assert res.len == counters.len
+}
+
+fn test_parallel_amap() {
+	input := [1, 2, 3, 4, 5, 6, 7, 8, 9]
+	dump(input)
+	dump(input.len)
+	output := parallel.amap(input, fn (i int) int {
+		delay := rand.intn(250) or { 250 }
+		time.sleep(delay * time.millisecond)
+		return i * i
+	})
+	dump(output)
+	dump(output.len)
+	assert input.len == output.len
+
+	for i, _ in output {
+		assert output[i] == input[i] * input[i]
+	}
+
+	// unordered output validation
+	assert output.len == input.len
+	op_sorted := output.sorted()
+	dump(op_sorted)
+	for i, op in op_sorted {
+		assert op == input[i] * input[i]
+	}
+}