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Groovy 学习笔记3 运行效率,
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第一篇笔记里面,我说groovy运行的居然还满快的,其实是个误会了。我上次做八皇后还是在8080上面用basic做的,和现在奔四上面的groovy相比是没有意义的。特地又做了个对比试验:
1

int
q
=
9
2

int
[] i
=
new
int
[q]
3

int
count
=
0
4

long
t
=
System.currentTimeMillis();
5

scan(
0
)
6

println(
"
totle results:
"
+
count)
7

println(
"
totle time:
"
+
(System.currentTimeMillis()
-
t));
8


def scan(n)
@H_404_148@
{
9

if (n==q)@H_404_148@
{
10
println(i.toList())
11
count++
12
return
13
}
14
i[n]=0
15

while(i[n]<q)@H_404_148@
{
16
i[n] = i[n]+1
17
if (check(n))
18
scan(n+1)
19
}
20
}
21


def check(n)
@H_404_148@
{
22
if (n>0)
23
for (j in 0..<n)
24
if (i[j]==i[n] || i[j]-i[n]==j-n || i[j]-i[n]==n-j )
25
return false
26
return true
27
}
运行结果是:totle time:7271 (为了用groovy控制台运行的,直接用groovy命令运行还要慢一点)
java呢?
queens.java:
1


public
class
queens
@H_404_148@
{
2
static int q=9;
3
static int[] i=new int[q];
4
static int count=0;
5

public static void main(String[] args)@H_404_148@
{
6
long t = System.currentTimeMillis();
7
scan(0);
8
System.out.println("totle results:"+count);
9
System.out.println("totle time:"+(System.currentTimeMillis()-t));
10
}
11

private static void scan(int n)@H_404_148@
{
12

if (n==q)@H_404_148@
{
13
for (int k=0;k<q;k++) System.out.print(i[k]+(k==q-1?"/n":","));
14
count++;
15
return;
16
}
17
i[n]=0;
18

while(i[n]<q)@H_404_148@
{
19
i[n] = i[n]+1;
20

if (check(n))@H_404_148@
{
21
scan(n+1);
22
}
23
}
24
}
25

private static boolean check(int n)@H_404_148@
{
26

for(int j=0;j<n;j++)@H_404_148@
{
27

if (i[j]==i[n] || i[j]-i[n]==j-n || i[j]-i[n]==n-j )@H_404_148@
{
28
return false;
29
}
30
}
31
return true;
32
}
33
}
34

运行结果是:totle time:271
每次运行花费的时间略有不同,groovy和java的运行速度看来大致相差10~30倍左右。
能说这是脚本语言天生的缺陷吗?我们来看看同样是类似java语法的脚本语言javascript在IE里面的速度:
1

var q
=
9
2

var i
=
[]
3

var count
=
0
4

var d
=
new
Date();
5

scan(
0
)
6

document.write(
"
totle results:
"
+
count
+
"
<br>
"
)
7

document.write(
"
time used:
"
+
(
new
Date()
-
d)
+
"
<br>
"
)
8

9


function scan(n)
@H_404_148@
{
10

if (n==q)@H_404_148@
{
11
document.write(i+"<br>")
12
count++
13
return
14
}
15
i[n]=0
16

while(i[n]<q)@H_404_148@
{
17
i[n] = i[n]+1
18

if (check(n))@H_404_148@
{
19
scan(n+1)
20
}
21
}
22
}
23

24


function check(n)
@H_404_148@
{
25
for (var j=0; j<n;j++)
26
if (i[j]==i[n] || i[j]-i[n]==j-n || i[j]-i[n]==n-j )
27
return false
28
return true
29
}
运行结果是: time used:1241
比groovy快了5倍以上。groovy可真是够慢的。
把groovy编译的class文件反编译了一下,看到groovy生成的代码效率确实是太低了,我们就看循环最内层的check函数吧:
1


def check(n)
@H_404_148@
{
2
if (n>0)
3
for (j in 0..<n)
4
if (i[j]==i[n] || i[j]-i[n]==j-n || i[j]-i[n]==n-j )
5
return false
6
return true
7
}
编译后变成
1

public
Object check(Object obj)
2


@H_404_148@
{
3
if(ScriptBytecodeAdapter.compareGreaterThan(obj, new Integer(0)))
4

@H_404_148@
{
5
Object obj1 = null;
6
for(Iterator iterator = ScriptBytecodeAdapter.asIterator(ScriptBytecodeAdapter.createRange(new Integer(0), obj, false)); iterator.hasNext();)
7

@H_404_148@
{
8
Object obj2 = iterator.next();
9
Object obj3 = null;
10

if(ScriptBytecodeAdapter.asBool(ScriptBytecodeAdapter.asBool(ScriptBytecodeAdapter.compareEqual(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, "i"), "getAt", ((Object) (new Object[] @H_404_148@
{
11
obj2
12

}))), ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, ((Object) (new Object[] @H_404_148@
{
13
obj
14

})))) || ScriptBytecodeAdapter.compareEqual(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, ((Object) (new Object[] @H_404_148@
{
15
obj2
16

}))), "minus", ((Object) (new Object[] @H_404_148@
{
17

ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, ((Object) (new Object[] @H_404_148@
{
18
obj
19
})))
20

}))), ScriptBytecodeAdapter.invokeMethod(obj2, ((Object) (new Object[] @H_404_148@
{
21
obj
22

})))) ? ((Object) (Boolean.TRUE)) : ((Object) (Boolean.FALSE))) || ScriptBytecodeAdapter.compareEqual(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, ((Object) (new Object[] @H_404_148@
{
23
obj2
24

}))), ((Object) (new Object[] @H_404_148@
@H_317_2404@{
25

ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, ((Object) (new Object[] @H_404_148@
{
26
obj
27
})))
28

}))), ScriptBytecodeAdapter.invokeMethod(obj, ((Object) (new Object[] @H_404_148@
{
29
obj2
30
})))) ? ((Object) (Boolean.TRUE)) : ((Object) (Boolean.FALSE))))
31
return Boolean.FALSE;
32
}
33
34
}
35
return Boolean.TRUE;
36
}
37

一切都是object,做任何事情都是invokeMethod,两个整数的比较居然要写将近400个字符的代码,光看代码量都可以吓倒我了。这是我们期待的脚本语言吗?
groovy可以嵌入到java代码里面,但是java代码可以嵌入到groovy里面吗?我觉得groovy有必要提供这样一种机制,在有必要的时候可以消除性能瓶颈。可是现在只看到groovy里面可以通过Scriptom(现在还是beta版)嵌入vbs、js脚本(包括使用WSH,FSO)或者调用InternetExplorer、Media Player、Word和Excel等windows组件。看来对消除性能瓶颈的帮助不大。