Matcher performance improvements

[Martin Buchholz]

Jeremy is out for a few days - let's pick this up next week.

In the meantime, we probably don't want
public Appendable appendTail(Appendable a) {

but instead

public <T extends Appendable> T appendTail(T a) {

It would be nice to be able to simply change the signature of the
existing method
that takes a StringBuffer, but there's no doubt some obscure
reason why that would not be 100% compatible.

Martin


> I suggested yesterday that you might consider to add the pair for the "Appendable" for more general use scenario,
> instead of the StringBuilder. I just tried your test case with this approach

> http://cr.openjdk.java.net/~sherman/regex_replace/webrev/src/share/classes/java/util/regex/Matcher.java.sdiff.html

> I still see 20%+ gain.

> The only trick is we will have to deal with the "IOException" from the Appendable append methods...


On Wed, Aug 12, 2009 at 18:56, Xueming Shen<Xueming.Shen at sun.com> wrote:
>
> The RFE#5066679 has been on my "next week's todo list" for a while:-) it
> looks like
> the Appendable might be a better choice here? I guess we should gain the
> same performance
> when you pass in a StringBuilder. Opinion?
>
> Sherman
>
> Martin Buchholz wrote:
>>
>> Hi regex/String team,
>>
>> We would like to contribute a performance improvement for Matcher.
>>
>> Please file a bug.
>>
>> category: java_util_regex
>> Synopsis: Faster Matcher by replacing StringBuffer with StringBuilder
>>
>> Description:
>> The old Matcher API and implementation depend on the old StringBuffer
>> class.
>> The use of StringBuilder gives measurable performance improvement in
>> real world applications.
>> http://cr.openjdk.java.net/~martin/webrevs/openjdk7/Matcher-perf/
>> Written by Jeremy Manson.
>>
>> Here's a microbenchmark, where it gives 25% win:
>>
>> public class StringReplace {
>>  static String jabber = "Twas brillig, and the slithy toves " +
>>      "Did gyre and gimble in the wabe; " +
>>      "All mimsy were the borogoves, " +
>>      "And the mome raths outgrabe. " +
>>      " " +
>>      "Beware the Jabberwock, my son! " +
>>      "The jaws that bite, the claws that catch! " +
>>      "Beware the Jubjub bird, and shun " +
>>      "The frumious Bandersnatch!" +
>>      " " +
>>      "He took his vorpal sword in hand: " +
>>      "Long time the manxome foe he sought— " +
>>      "So rested he by the Tumtum tree, " +
>>      "And stood awhile in thought. " +
>>      " " +
>>      "And as in uffish thought he stood, " +
>>      "The Jabberwock, with eyes of flame, " +
>>      "Came whiffling through the tulgey wood, " +
>>      "And burbled as it came! " +
>>      " " +
>>      "One, two! One, two! and through and through " +
>>      "The vorpal blade went snicker-snack! " +
>>      "He left it dead, and with its head " +
>>      "He went galumphing back. " +
>>      " " +
>>      "And hast thou slain the Jabberwock? " +
>>      "Come to my arms, my beamish boy! " +
>>      "O frabjous day! Callooh! Callay!" +" " +
>>      "He chortled in his joy. " +
>>      " " +
>>      "'Twas brillig, and the slithy toves " +
>>      "Did gyre and gimble in the wabe; " +
>>      "All mimsy were the borogoves, " +
>>      "And the mome raths outgrabe?";
>>
>>  public static void replace() {
>>    long start = System.currentTimeMillis();
>>    for (int i = 0; i < 100000; i++) {
>>      jabber.replaceAll("the", "ze");
>>    }
>>    long stop = System.currentTimeMillis();
>>    System.out.println(stop);
>>    System.out.println(start);
>>
>>    System.out.println(stop - start);
>>  }
>>
>>  public static void main(String[] args) {
>>    for (int i = 0; i < 5; i++) {
>>      replace();
>>    }
>>  }
>> }
>>
>
>