[jira] Closed: (HARMONY-589) [classlib][luni] java.lang.StringBuilder performs very slowly

["Nathan Beyer (JIRA)" <ji...@apache.org>]

     [ http://issues.apache.org/jira/browse/HARMONY-589?page=all ]
     
Nathan Beyer closed HARMONY-589:
--------------------------------


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> [classlib][luni] java.lang.StringBuilder performs very slowly
> -------------------------------------------------------------
>
>          Key: HARMONY-589
>          URL: http://issues.apache.org/jira/browse/HARMONY-589
>      Project: Harmony
>         Type: Improvement

>   Components: Classlib
>     Reporter: Alexey Varlamov
>     Assignee: Nathan Beyer
>     Priority: Minor
>  Attachments: AbstractStringBuilder.java, SB.diff
>
> The j.l.StringBuilder was introduced in Java 1.5 mainly as a speedup replacement to heavily synchronized j.l.StringBuffer. 
> However, current implementation of StringBuilder performs 2-4 times slower than StringBuffer. 
> The following simple test demonstrates this:
> public class SPTest {
>  public static void main(String[] s) {
>   test1();
>   test2();
>  }
>  
>  static void test1() {
>   long t1 = System.currentTimeMillis();
>   StringBuilder sb1 = new StringBuilder(100000);
>   for(int i=0; i<10000; i++){
>     sb1.append("0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789");
>   }
>   long t2 = System.currentTimeMillis();
>   
>   StringBuffer sb2 = new StringBuffer(100000);
>   for(int i=0; i<10000; i++){
>     sb2.append("0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789");
>   }
>   long t3 = System.currentTimeMillis();
>   
>   System.out.println("append(String) test, ms");
>   System.out.println("\tStringBuilder : " + (t2-t1));
>   System.out.println("\tStringBuffer : " + (t3-t2));
>  }
>  
>  static void test2() {
>   long t1 = System.currentTimeMillis();
>   String s1 = "0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789";
>   for(int i=0; i<1000; i++){
>     s1 = new StringBuilder(s1).append("1234567890").toString();
>   }
>   long t2 = System.currentTimeMillis();
>   String s2 = "0123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789";
>   for(int i=0; i<1000; i++){
>     s2 = new StringBuffer(s2).append("1234567890").toString();
>   }
>   long t3 = System.currentTimeMillis();
>   System.out.println("constructor(String) test, ms");
>   System.out.println("\tStringBuilder : " + (t2-t1));
>   System.out.println("\tStringBuffer : " + (t3-t2));
>  }
> }
> Typical output on J9vm, interpreter mode:
> ---------------------------------
> append(String) test, ms
>  StringBuilder : 221
>  StringBuffer : 140
> constructor(String) test, ms
>  StringBuilder : 1051
>  StringBuffer : 291
> ---------------------------------
> J9vm, JIT mode:
> ---------------------------------
> append(String) test, ms
>  StringBuilder : 80
>  StringBuffer : 30
> constructor(String) test, ms
>  StringBuilder : 130
>  StringBuffer : 40
> --------------------------------
> Jrockit 1.5.0 output:
> --------------------------------
> append(String) test, ms
>  StringBuilder : 10
>  StringBuffer : 20
> constructor(String) test, ms
>  StringBuilder : 30
>  StringBuffer : 40
> Patch to fix this will follow.

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