Example

go.mod

@@ -2,4 +2,4 @@ module git.tuxpa.in/a/lambda
 
 go 1.18
 
-require golang.org/x/exp v0.0.0-20220325121720-054d8573a5d8 // indirect
+require golang.org/x/exp v0.0.0-20220325121720-054d8573a5d8

parallel/map.go

@@ -6,8 +6,12 @@ import (
 	"git.tuxpa.in/a/lambda"
 )
 
-func Map[T any](xs []T, fx func(T) T) []T {
+func Map[T any](xs []T, fx func(T) T, n ...int) []T {
-	spl := lambda.Split(xs, routineCount)
+	rc := routineCount
+	if len(n) > 0 {
+		rc = n[0]
+	}
+	spl := lambda.Split(xs, rc)
 	wg := new(sync.WaitGroup)
 	wg.Add(len(spl))
 	for i, v := range spl {
@@ -20,8 +24,12 @@ func Map[T any](xs []T, fx func(T) T) []T {
 	return lambda.Flatten(spl)
 }
 
-func MapV[T, V any](xs []T, fx func(T) V) []V {
+func MapV[T, V any](xs []T, fx func(T) V, n ...int) []V {
-	spl := lambda.Split(xs, routineCount)
+	rc := routineCount
+	if len(n) > 0 {
+		rc = n[0]
+	}
+	spl := lambda.Split(xs, rc)
 	wg := new(sync.WaitGroup)
 	wg.Add(len(spl))
 	tmp := make([][]V, len(spl))
@@ -34,3 +42,42 @@ func MapV[T, V any](xs []T, fx func(T) V) []V {
 	wg.Wait()
 	return lambda.Flatten(tmp)
 }
+
+func MapError[T any](xs []T, fx func(T) (T, error), n ...int) ([]T, []error) {
+	rc := routineCount
+	if len(n) > 0 {
+		rc = n[0]
+	}
+	spl := lambda.Split(xs, rc)
+	wg := new(sync.WaitGroup)
+	wg.Add(len(spl))
+	tmp := make([][]error, len(spl))
+	for i, v := range spl {
+		go func(ix int, vx []T) {
+			spl[ix], tmp[ix] = lambda.MapError(vx, fx)
+			wg.Done()
+		}(i, v)
+	}
+	wg.Wait()
+	return lambda.Flatten(spl), lambda.Flatten(tmp)
+}
+
+func MapErrorV[T, V any](xs []T, fx func(T) (V, error), n ...int) ([]V, []error) {
+	rc := routineCount
+	if len(n) > 0 {
+		rc = n[0]
+	}
+	spl := lambda.Split(xs, rc)
+	wg := new(sync.WaitGroup)
+	wg.Add(len(spl))
+	tmp := make([][]V, len(spl))
+	tmp2 := make([][]error, len(spl))
+	for i, v := range spl {
+		go func(ix int, vx []T) {
+			tmp[ix], tmp2[ix] = lambda.MapErrorV(vx, fx)
+			wg.Done()
+		}(i, v)
+	}
+	wg.Wait()
+	return lambda.Flatten(tmp), lambda.Flatten(tmp2)
+}

parallel/parallel.go

@@ -1,9 +1,6 @@
 package parallel
 
-import (
+var routineCount int = 4
-)
-
-var routineCount int = 1
 
 func SetRoutineCount(n int) {
 	routineCount = n

parallel/request_test.go

@@ -0,0 +1,74 @@
+package parallel_test
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"testing"
+
+	"git.tuxpa.in/a/lambda/parallel"
+)
+
+var requests = make([]*http.Request, 20)
+
+func init() {
+	for i := range requests {
+		r, _ := http.NewRequest("GET", fmt.Sprintf("https://jsonplaceholder.typicode.com/todos/%d", i), nil)
+		requests[i] = r
+	}
+}
+
+type someResult struct {
+	Title string `json:"title"`
+	Id    int    `json:"id"`
+}
+
+func TestParallelRequest4Routine(t *testing.T) {
+	results, errs := parallel.MapErrorV(requests, func(r *http.Request) (*someResult, error) {
+		out := &someResult{}
+		res, err := http.DefaultClient.Do(r)
+		if err != nil {
+			return nil, err
+		}
+		defer res.Body.Close()
+		err = json.NewDecoder(res.Body).Decode(out)
+		return out, err
+	}, 4)
+	for i, v := range results {
+		if errs[i] != nil {
+			t.Logf("err: %s", errs[i])
+		} else {
+			t.Logf("result: %+v", v)
+		}
+	}
+}
+
+func BenchmarkParallelRequest1Routine(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		parallel.MapErrorV(requests, func(r *http.Request) (*someResult, error) {
+			out := &someResult{}
+			res, err := http.DefaultClient.Do(r)
+			if err != nil {
+				return nil, err
+			}
+			defer res.Body.Close()
+			err = json.NewDecoder(res.Body).Decode(out)
+			return out, err
+		}, 1)
+	}
+}
+
+func BenchmarkParallelRequest4Routine(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		parallel.MapErrorV(requests, func(r *http.Request) (*someResult, error) {
+			out := &someResult{}
+			res, err := http.DefaultClient.Do(r)
+			if err != nil {
+				return nil, err
+			}
+			defer res.Body.Close()
+			err = json.NewDecoder(res.Body).Decode(out)
+			return out, err
+		}, 4)
+	}
+}