author | Christian Urban <christian dot urban at kcl dot ac dot uk> |
Tue, 20 Sep 2016 12:13:11 +0100 | |
changeset 420 | 25bc57b32efa |
parent 412 | 1cef3924f7a2 |
child 474 | 4bdf0dedd708 |
permissions | -rw-r--r-- |
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// a case of catastrophic backtracking in Java |
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// |
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// regexp: (a*)*b |
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// strings: aa.... |
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import java.util.regex.*; |
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public class catastrophic { |
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public static void main(String[] args) { |
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//we always run all the tests twice -> warmup of the JVM |
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for (int runs = 0; runs < 2; runs++) { |
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Pattern pattern = Pattern.compile("(a*)*b"); |
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|
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// Run from 5 to 28 characters |
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for (int length = 5; length < 28; length++) { |
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// Build input of specified length |
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String input = ""; |
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for (int i = 0; i < length; i++) { input += "a"; } |
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// Measure the average duration of two calls... |
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long start = System.nanoTime(); |
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for (int i = 0; i < 2; i++) { |
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pattern.matcher(input).find(); |
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} |
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System.out.println(length + " " + input + ": " |
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+ ((System.nanoTime() - start) / 2000000000d) |
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+ "s"); |
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} |
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} |
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} |
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} |