add square root performance test

Author: LuigiAndrea

Diff for: column7-back-envelope/square-root-perf/square-root.go

@@ -0,0 +1,23 @@
+package squareroot
+
+import (
+	"math"
+)
+
+func squareRoot(n int) float64 {
+	var fa float64
+	for i := 0; i < n; i++ {
+		fa = math.Sqrt(10.0)
+	}
+
+	return fa
+}
+
+func squareRootVariable(n int) float64 {
+	var fa float64
+	for i := 0; i < n; i++ {
+		fa = math.Sqrt(float64(i))
+	}
+
+	return fa
+}

Diff for: column7-back-envelope/square-root-perf/square-root_test.go

@@ -0,0 +1,22 @@
+// +build all column7 squareroot square root perf
+
+package squareroot
+
+import (
+	"testing"
+
+	"github.com/LuigiAndrea/GoPearls/utilities"
+	goth "github.com/LuigiAndrea/test-helper/messages"
+)
+
+var steps int = 1000000000
+
+func TestCallSquareRoot(t *testing.T) {
+	defer utilities.Elapse(goth.GetFuncName(squareRoot))()
+	squareRoot(steps)
+}
+
+func TestCallSquareRootVariable(t *testing.T) {
+	defer utilities.Elapse(goth.GetFuncName(squareRootVariable))()
+	squareRootVariable(steps)
+}

Diff for: utilities/helper.go

@@ -1,7 +1,9 @@
 package utilities
 
 import (
+	"fmt"
 	"sort"
+	"time"
 )
 
 //Reverse a slice
@@ -26,3 +28,12 @@ func PreAppend(list []interface{}, elements ...interface{}) []interface{} {
 	}
 	return list
 }
+
+//Elapse calculate the time elapsed
+func Elapse(name string) func() {
+	start := time.Now()
+
+	return func() {
+		fmt.Printf("%s took %v\n", name, time.Since(start))
+	}
+}