adding benchmarks

Dockerfile

@@ -3,6 +3,6 @@ FROM golang:1.18rc1-bullseye
 
 WORKDIR /go/src/github.com/samber/lo
 
-COPY Makefile go.* /go/src/github.com/samber/lo
+COPY Makefile go.* /go/src/github.com/samber/lo/
 
 RUN make tools

Makefile

@@ -15,7 +15,9 @@ watch-test:
 	reflex -R assets.go -t 50ms -s -- sh -c 'gotest -v ./...'
 
 bench:
-	gotest -benchmem -bench ./...
+	go test -benchmem -count 3 -bench ./...
+watch-bench:
+	reflex -R assets.go -t 50ms -s -- sh -c 'go test -benchmem -count 3 -bench ./...'
 
 coverage:
 	${BIN} test -v -coverprofile cover.out .

README.md

@@ -574,9 +574,42 @@ ptr := lo.ToSlicePtr[string]([]string{"hello", "world"})
 // []*string{"hello", "world"}
 ```
 
-## 🛩 Performance
+## 🛩 Benchmark
+
+We executed a simple benchmark with the a dead-simple `lo.Map` loop:
+
+See the full implementation [here](./benchmark_test.go).
+
+```go
+_ = lo.Map[int64](arr, func(x int64, i int) string {
+    return strconv.FormatInt(x, 10)
+})
+```
+
+**Result:**
+
+Here is a comparison between `lo.Map`, `lop.Map`, `go-funk` library and a simple Go `for` loop.
+
+```
+$ go test -benchmem -bench ./...
+goos: linux
+goarch: amd64
+pkg: github.com/samber/lo
+cpu: Intel(R) Core(TM) i5-7267U CPU @ 3.10GHz
+BenchmarkMap/lo.Map-8         	       8	 131041218 ns/op	39998055 B/op	 1000001 allocs/op
+BenchmarkMap/lop.Map-8        	       2	 509805437 ns/op	120018304 B/op	 3000214 allocs/op
+BenchmarkMap/reflect-8        	       2	 840512374 ns/op	170325888 B/op	 4000042 allocs/op
+BenchmarkMap/for-8            	       9	 127074794 ns/op	39998040 B/op	 1000001 allocs/op
+PASS
+ok  	github.com/samber/lo	7.531s
+```
+
+- `lo.Map` is way faster (x7) than `go-funk`, a relection-based Map implementation.
+- `lo.Map` have the same allocation profile than `for`.
+- `lo.Map` is 4% slower than `for`.
+- `lop.Map` is slower than `lo.Map` because it implies more memory allocation and locks. `lop.Map` will be usefull for long-running callbacks, such as i/o bound processing.
+- `for` beats other implementations for memory and CPU.
 
-// TODO
 
 ## 🤝 Contributing
 

go.mod

@@ -7,5 +7,6 @@ require github.com/stretchr/testify v1.7.0
 require (
 	github.com/davecgh/go-spew v1.1.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/thoas/go-funk v0.9.1 // indirect
 	gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c // indirect
 )

go.sum

@@ -3,9 +3,13 @@ github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=
 github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/thoas/go-funk v0.9.1 h1:O549iLZqPpTUQ10ykd26sZhzD+rmR5pWhuElrhbC20M=
+github.com/thoas/go-funk v0.9.1/go.mod h1:+IWnUfUmFO1+WVYQWQtIJHeRRdaIyyYglZN7xzUPe4Q=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=