I have tested several simple functions with Golang and Java. To my
surprise, Java sometimes is faster than Golang（especially in recursive
function and some function in standard library such as math/rand.Rand）. I
wonder why. Here is some code I used for test and the result.
Golang code:
package main
import (
"fmt"
"math/rand"
"time"
)
func calPi(pointCount int) float64 {
inCircleCount := 0
var x, y float64
var Pi float64
for i := 0; i < pointCount; i++ {
x = rand.Float64()
y = rand.Float64()
if x*x+y*y < 1 {
inCircleCount++
}
}
Pi = (4.0 * float64(inCircleCount)) / float64(pointCount)
return Pi
}
func fibonacci(c int64) int64 {
if c < 2 {
return c
}
return fibonacci(c-2) + fibonacci(c-1)
}
func main() {
rand.Seed(time.Now().Unix()) // 初始化随机数
fmt.Printf("Test 1\n")
startTime := time.Now()
result := 0.0
for i := 0.0; i < 1000000000; i = i + 1 {
result += i * i
}
endTime := time.Now()
fmt.Printf("Result: %v\n", result)
fmt.Printf("Duration: %v\n", endTime.Sub(startTime))
fmt.Printf("Test 2\n")
startTime = time.Now()
resultInt := fibonacci(50)
endTime = time.Now()
fmt.Printf("Result: %v\n", resultInt)
fmt.Printf("Duration: %v\n", endTime.Sub(startTime))
fmt.Printf("Test 3\n")
startTime = time.Now()
result = 0.0
for i := 0.0; i < 100000000; i = i + 1 {
result += rand.Float64()
}
endTime = time.Now()
fmt.Printf("Result: %v\n", result)
fmt.Printf("Duration: %v\n s", endTime.Sub(startTime))
fmt.Printf("Test 4\n")
startTime = time.Now()
result = calPi(100000000)
endTime = time.Now()
fmt.Printf("Result: %v\n", result)
fmt.Printf("Duration: %v s\n", endTime.Sub(startTime))
}
the result:
Test 1
Result: 3.333333328333552e+26
Duration: 1.449212507s
Test 2
Result: 12586269025
Duration: 1m31.645050682s
Test 3
Result: 4.999483069673434e+07
Duration: 2.534121566s
sTest 4
Result: 3.14147056
Duration: 5.036491495s s
Java code:
public class Performance {
public static double calPi(int pointCount) {
int inCircleCount = 0;
double x, y;
double Pi;
for (int i = 0; i < pointCount; i++) {
x = Math.random();
y = Math.random();
if (x * x + y * y < 1) {
inCircleCount++;
}
}
Pi = (4.0 * inCircleCount) / pointCount;
return Pi;
}
public static double cal(double a, double b, double c) {
return a * b / (c + 1) + a;
}
public static long fibonacci(long c) {
if (c < 2)
return c;
return fibonacci(c - 2) + fibonacci(c - 1);
}
public static void main(String[] args) {
System.out.println("Test 1");
long startTime = System.currentTimeMillis();
double result = 0.0;
for (double i = 0.0; i < 1000000000; i = i + 1) {
result += i * i;
}
long endTime = System.currentTimeMillis();
float duration = (float) (endTime - startTime) / 1000;
System.out.println("Result: " + result);
System.out.println("Duration: " + duration + " s");
System.out.println("Test 2");
startTime = System.currentTimeMillis();
long resultInt = fibonacci(50);
endTime = System.currentTimeMillis();
duration = (float) (endTime - startTime) / 1000;
System.out.println("Result: " + resultInt);
System.out.println("Duration: " + duration + " s");
System.out.println("Test 3");
startTime = System.currentTimeMillis();
result = 0.0;
for (double i = 0; i < 100000000; i = i + 1) {
result += Math.random();
}
endTime = System.currentTimeMillis();
duration = (float) (endTime - startTime) / 1000;
System.out.println("Result: " + result);
System.out.println("Duration: " + duration + " s");
System.out.println("Test 4");
startTime = System.currentTimeMillis();
result = calPi(100000000);
endTime = System.currentTimeMillis();
duration = (float) (endTime - startTime) / 1000;
System.out.println("Result: " + result);
System.out.println("Duration: " + duration + " s");
}
}
result:
Test 1
Result: 3.333333328333552E26
Duration: 2.948 s
Test 2
Result: 12586269025
Duration: 60.816 s
Test 3
Result: 4.9999087237930864E7
Duration: 2.448 s
Test 4
Result: 3.14147284
Duration: 4.786 s
The difference of Test 2 results really shocked me!
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