[jira] [Commented] (LUCENE-7525) ASCIIFoldingFilter.foldToASCII performance issue due to large compiled method size

["Adrien Grand (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LUCENE-7525?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15612135#comment-15612135 ] 

Adrien Grand commented on LUCENE-7525:
--------------------------------------

This is probably one of the most used token filters, so +1 to explore if/how we can make it faster. Maybe we should add an analyzer that has case folding enabled to http://people.apache.org/~mikemccand/lucenebench/analyzers.html.

> ASCIIFoldingFilter.foldToASCII performance issue due to large compiled method size
> ----------------------------------------------------------------------------------
>
>                 Key: LUCENE-7525
>                 URL: https://issues.apache.org/jira/browse/LUCENE-7525
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: modules/analysis
>    Affects Versions: 6.2.1
>            Reporter: Karl von Randow
>
> The {{ASCIIFoldingFilter.foldToASCII}} method has an enormous switch statement and is too large for the HotSpot compiler to compile; causing a performance problem.
> The method is about 13K compiled, versus the 8KB HotSpot limit. So splitting the method in half works around the problem.
> In my tests splitting the method in half resulted in a 5X performance increase.
> In the test code below you can see how slow the fold method is, even when it is using the shortcut when the character is less than 0x80, compared to an inline implementation of the same shortcut.
> So a workaround is to split the method. I'm happy to provide a patch. It's a hack, of course. Perhaps using the {{MappingCharFilterFactory}} with an input file as per SOLR-2013 would be a better replacement for this method in this class?
> {code:java}
> public class ASCIIFoldingFilterPerformanceTest {
> 	private static final int ITERATIONS = 1_000_000;
> 	@Test
> 	public void testFoldShortString() {
> 		char[] input = "testing".toCharArray();
> 		char[] output = new char[input.length * 4];
> 		for (int i = 0; i < ITERATIONS; i++) {
> 			ASCIIFoldingFilter.foldToASCII(input, 0, output, 0, input.length);
> 		}
> 	}
> 	@Test
> 	public void testFoldShortAccentedString() {
> 		char[] input = "éúéúøßüäéúéúøßüä".toCharArray();
> 		char[] output = new char[input.length * 4];
> 		for (int i = 0; i < ITERATIONS; i++) {
> 			ASCIIFoldingFilter.foldToASCII(input, 0, output, 0, input.length);
> 		}
> 	}
> 	@Test
> 	public void testManualFoldTinyString() {
> 		char[] input = "t".toCharArray();
> 		char[] output = new char[input.length * 4];
> 		for (int i = 0; i < ITERATIONS; i++) {
> 			int k = 0;
> 			for (int j = 0; j < 1; ++j) {
> 				final char c = input[j];
> 				if (c < '\u0080') {
> 					output[k++] = c;
> 				} else {
> 					Assert.assertTrue(false);
> 				}
> 			}
> 		}
> 	}
> }
> {code}



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