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Posted to dev@poi.apache.org by GitBox <gi...@apache.org> on 2021/01/15 06:13:35 UTC

[GitHub] [poi] cor3000 opened a new pull request #215: reuse pre-compiled regex

cor3000 opened a new pull request #215:
URL: https://github.com/apache/poi/pull/215


   improves parseDouble performance by about 85%-90%
   100000 invocations 
   before ~230ms 
   after ~28ms (using a precompiled regex)
   
   I am not sure how to add a meaningful performance unit test for this in this project.
   
   Here my local test printing comparing the two different method implementations:
   
   ```
   import org.junit.Test;
   
   import java.util.regex.Pattern;
   
   public class TestParseDoublePerformance {
   
   	private static final String fpRegex = "[\\x00-\\x20]*[+-]?(((((\\p{Digit}+)(\\.)?((\\p{Digit}+)?)([eE][+-]?(\\p{Digit}+))?)|(\\.((\\p{Digit}+))([eE][+-]?(\\p{Digit}+))?))))[\\x00-\\x20]*";
   	private static final Pattern fpPattern = Pattern.compile(fpRegex);
   
   	@Test
   	public void testPerformance() {
   		long start;
   		for (int j = 0; j < 10; j++) {
   			start = System.nanoTime();
   			for(int i = 0; i < 100000; i++) {
   				parseDouble(1000 + ".1234" + i);
   			}
   			System.out.println("100000 x Pattern.matches(fpRegex, pText)   : " + ((System.nanoTime() - start) / 1000000.0) + "ms");
   
   			start = System.nanoTime();
   			for(int i = 0; i < 100000; i++) {
   				parseDouble2(1000 + ".1234" + i);
   			}
   			System.out.println("100000 x fpPattern.matcher(pText).matches(): " + ((System.nanoTime() - start) / 1000000.0) + "ms");
   		}
   	}
   
   	public static Double parseDouble(String pText) {
   		if (Pattern.matches(fpRegex, pText)) {
   			try {
   				return Double.parseDouble(pText);
   			} catch (NumberFormatException var2) {
   				return null;
   			}
   		} else {
   			return null;
   		}
   	}
   
   	public static Double parseDouble2(String pText) {
   		if (fpPattern.matcher(pText).matches()) {
   			try {
   				return Double.parseDouble(pText);
   			} catch (NumberFormatException var2) {
   				return null;
   			}
   		} else {
   			return null;
   		}
   	}
   }
   ```
   
   Output (using jdk 11)
   ```
   100000 x Pattern.matches(fpRegex, pText)   : 528.583911ms
   100000 x fpPattern.matcher(pText).matches(): 36.131033ms
   100000 x Pattern.matches(fpRegex, pText)   : 247.689554ms
   100000 x fpPattern.matcher(pText).matches(): 28.203332ms
   100000 x Pattern.matches(fpRegex, pText)   : 230.243142ms
   100000 x fpPattern.matcher(pText).matches(): 28.258646ms
   100000 x Pattern.matches(fpRegex, pText)   : 246.361356ms
   100000 x fpPattern.matcher(pText).matches(): 28.530509ms
   100000 x Pattern.matches(fpRegex, pText)   : 232.466833ms
   100000 x fpPattern.matcher(pText).matches(): 29.992254ms
   100000 x Pattern.matches(fpRegex, pText)   : 232.972345ms
   100000 x fpPattern.matcher(pText).matches(): 27.680976ms
   100000 x Pattern.matches(fpRegex, pText)   : 227.946587ms
   100000 x fpPattern.matcher(pText).matches(): 28.363269ms
   100000 x Pattern.matches(fpRegex, pText)   : 235.331679ms
   100000 x fpPattern.matcher(pText).matches(): 27.830178ms
   100000 x Pattern.matches(fpRegex, pText)   : 233.785736ms
   100000 x fpPattern.matcher(pText).matches(): 29.759473ms
   100000 x Pattern.matches(fpRegex, pText)   : 231.619982ms
   100000 x fpPattern.matcher(pText).matches(): 28.545904ms
   ```
   


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[GitHub] [poi] asfgit closed pull request #215: Improve Performance of OperandResolver#parseDouble

Posted by GitBox <gi...@apache.org>.
asfgit closed pull request #215:
URL: https://github.com/apache/poi/pull/215


   


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[GitHub] [poi] pjfanning commented on pull request #215: Improve Performance of OperandResolver#parseDouble

Posted by GitBox <gi...@apache.org>.
pjfanning commented on pull request #215:
URL: https://github.com/apache/poi/pull/215#issuecomment-762280392


   Thanks. Merged with 06ea5ad
   Will appear in v5.0.1 release


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