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regexp: regex is much slower than java #16758

liketic opened this issue Aug 17, 2016 · 2 comments

regexp: regex is much slower than java #16758

liketic opened this issue Aug 17, 2016 · 2 comments


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@liketic liketic commented Aug 17, 2016

Please answer these questions before submitting your issue. Thanks!

  1. What version of Go are you using (go version)?
    go1.6 darwin/amd64
  2. What operating system and processor architecture are you using (go env)?
  3. What did you do?
    If possible, provide a recipe for reproducing the error.
    A complete runnable program is good.
    A link on is best.

I found Go regex is too slow. I compared the regex perf between java and Go:
Go code:

text := "$value1$;$value2$;$value3$"
    for i := 0; i < 1000000; i++ {
        match := pattern.FindAllStringSubmatch(text, -1)
        for _, _ = range match {

Java code:

        String value = "$value1$;$value2$;$value3$";
        for (int i = 0; i < 1000000; i++) {
            Matcher matcher = pattern.matcher(value);
            while (matcher.find()) {
                // do nothing

Go costs 2.702s and Java costs 472ms.

  1. What did you expect to see?
    I think Go regex should not slower than Java so much.
  2. What did you see instead?
    Go regex is much slower than Java.
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@rakyll rakyll commented Aug 17, 2016

Go regex is known to be slower than Java (such as [1]). Is there a recent case you are reporting where you have seen a major perf downgrade or are you talking about the general case where Go is known to be slower?

I don't know the current involvement but making the regex more performant is a long-shot goal, not sure we can keep track of it under an issue on the tracker.


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@bradfitz bradfitz commented Aug 17, 2016

There are more concrete bugs tracking this... #15643, #13288, #11646, etc.

Closing this as a dup.

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4 participants