[jira] Commented: (HARMONY-5900) [classlib][pack200] CpBands.parseCpSignature(Ljava/io/InputStream;) is hot

["Aleksey Shipilev (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HARMONY-5900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12611273#action_12611273 ] 

Aleksey Shipilev commented on HARMONY-5900:
-------------------------------------------

Andrew, why does searching is done over String[] anyway? You get O(n) here.
Is there any opportunity to use HashMap/TreeMap?

> [classlib][pack200] CpBands.parseCpSignature(Ljava/io/InputStream;) is hot
> --------------------------------------------------------------------------
>
>                 Key: HARMONY-5900
>                 URL: https://issues.apache.org/jira/browse/HARMONY-5900
>             Project: Harmony
>          Issue Type: Wish
>          Components: Classlib
>    Affects Versions: 5.0M6
>         Environment: All Pack200 HEAD
>            Reporter: Andrew Cornwall
>
> The method org/apache/harmony/unpack200/CpBands.parseCpSignature(Ljava/io/InputStream;) appears to be very hot. I tried initially to optimize it by caching some of its arrays:
>     static void clearArrayCache() {
>     	arrayCache = new SegmentConstantPoolArrayCache();
>     }
>     
>     private static SegmentConstantPoolArrayCache arrayCache = new SegmentConstantPoolArrayCache();
>     
>     private int search(String[] array, String string) {
>     	if(array.length > 30) {
>     		List indexes = arrayCache.indexesForArrayKey(array, string);
>     		if (indexes.size() == 0) {
>     			return -1;
>     		}
>     		return ((Integer)indexes.get(0)).intValue();
>     	} else {
>     		for (int i = 0; i < array.length; i++) {
>     			if(array[i].equals(string)) {
>     				return i;
>     			}
>     		}
>     		return -1;
>     	}
>     }
> ... but that didn't appear to increase performance. (Maybe all the searches are done once?)
> Any ideas how to tune parseCpSignature to get it faster?

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