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: 1int q=9 2int[] i=new int[q] 3int count=0 4long t = System.currentTimeMillis(); 5scan(0) 6println("totle results:"+count) 7println("totle time:"+(System.currentTimeMillis()-t)); 8def scan(n){ 9 if (n==q){ 10 println(i.toList()) 11 count++ 12 return 13 } 14 i[n]=0 15 while(i[n]<q){ 16 i[n] = i[n]+1 17 if (check(n)) 18 scan(n+1) 19 } 20} 21def check(n){ 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: 1public class queens { 2 static int q=9; 3 static int[] i=new int[q]; 4 static int count=0; 5 public static void main(String[] args){ 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){ 12 if (n==q){ 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){ 19 i[n] = i[n]+1; 20 if (check(n)){ 21 scan(n+1); 22 } 23 } 24 } 25 private static boolean check(int n){ 26 for(int j=0;j<n;j++){ 27 if (i[j]==i[n] || i[j]-i[n]==j-n || i[j]-i[n]==n-j ){ 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:
1var q=9 2var i=[] 3var count=0 4var d = new Date(); 5scan(0) 6document.write("totle results:"+count+"<br>") 7document.write("time used:"+(new Date()-d)+"<br>") 8 9function scan(n){ 10 if (n==q){ 11 document.write(i+"<br>") 12 count++ 13 return 14 } 15 i[n]=0 16 while(i[n]<q){ 17 i[n] = i[n]+1 18 if (check(n)){ 19 scan(n+1) 20 } 21 } 22} 23 24function check(n){ 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:
1def check(n){ 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 { 3 if(ScriptBytecodeAdapter.compareGreaterThan(obj, new Integer(0))) 4 { 5 Object obj1 = null; 6 for(Iterator iterator = ScriptBytecodeAdapter.asIterator(ScriptBytecodeAdapter.createRange(new Integer(0), obj, false)); iterator.hasNext();) 7 { 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[] { 11 obj2 12}))), ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, "i"), "getAt", ((Object) (new Object[] { 13 obj 14})))) || ScriptBytecodeAdapter.compareEqual(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, "i"), "getAt", ((Object) (new Object[] { 15 obj2 16}))), "minus", ((Object) (new Object[] { 17 ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, "i"), "getAt", ((Object) (new Object[] { 18 obj 19 }))) 20}))), ScriptBytecodeAdapter.invokeMethod(obj2, "minus", ((Object) (new Object[] { 21 obj 22})))) ? ((Object) (Boolean.TRUE)) : ((Object) (Boolean.FALSE))) || ScriptBytecodeAdapter.compareEqual(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, "i"), "getAt", ((Object) (new Object[] { 23 obj2 24}))), "minus", ((Object) (new Object[] { 25 ScriptBytecodeAdapter.invokeMethod(ScriptBytecodeAdapter.getGroovyObjectProperty(this, "i"), "getAt", ((Object) (new Object[] { 26 obj 27 }))) 28}))), ScriptBytecodeAdapter.invokeMethod(obj, "minus", ((Object) (new Object[] { 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。
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