正则表达式在中的性能。NET vs Java

1 年，11 月 Questions & Answers 302

我在解析大型文本文件时遇到了正则表达式性能问题
我正在使用。NET 4.0，代码如下：

private static pattern = @"((\D|^)(19|20|)\d\d([- /.\\])(0[1-9]|1[012]|[1-9])\4(0[1-9]|[12][0-9]|3[01]|[0-9]) (\D|$))|" + @"((\D|^)(19|20|)\d\d([- /.\\])(0[1-9]|[12][0-9]|3[01]|[0-9])\11(0[1-9]|1[012]|[0-9]) (\D|$))|" + @"((\D|^)(0[1-9]|1[012]|[0-9])([- /.\\])(0[1-9]|[12][0-9]|3[01]|[0-9])\18(19|20|)\d\d(\D|$))|" + @"((\D|^)(0[1-9]|[12][0-9]|3[01]|[0-9])([- /.\\])(0[1-9]|1[012]|[0-9])\25(19|20|)\d\d(\D|$))|" + @"((\D|^)(19|20|)\d\d(0[1-9]|1[012])(0[1-9]|[12][0-9]|3[01])(\D|$))|" + @"((\D|^)(19|20|)\d\d(0[1-9]|[12][0-9]|3[01])(0[1-9]|1[012])(\D|$))|" + @"((\D|^)(0[1-9]|1[012])(0[1-9]|[12][0-9]|3[01])(19|20|)\d\d(\D|$))|" + @"((\D|^)(0[1-9]|[12][0-9]|3[01])(0[1-9]|1[012])(19|20|)\d\d(\D|$))|" + @"((^|(?<!(\d[- /.\\\d])|\d))(19|20|)\d\d([- /.\\])(0[1-9]|1[012]|[1-9])([^- /.\\\d\w]|$|\s))|" + @"((^|(?<!(\d[- /.\\\d])|\d))(0[1-9]|1[012]|[1-9])([- /.\\])(19|20|)\d\d([^- /.\\\d\w]|$|\s))|" + @"((^|(?<!(\d[- /.\\\d])|\d))(0[1-9]|1[012]|[1-9])([- /.\\])(0[1-9]|[12][0-9]|3[01])([^- /.\\\d\w]|$|\s))|" + @"((^|(?<!(\d[- /.\\\d])|\d))(0[1-9]|[12][0-9]|3[01])([- /.\\])(0[1-9]|1[012]|[1-9])([^- /.\\\d\w]|$|\s))"; private static Regex dateRegex = new new Regex(pattern, RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.IgnorePatternWhitespace | RegexOptions.Multiline); public static void Extract(string text) { foreach (Match match in dateRegex.Matches(text)) Console.Writeline("Match {0}",match.Value); }

包含200个匹配项的1MB文本文件的处理时间约为22秒
用Java运行相同的正则表达式会产生更快的结果：~13秒
我成功地缩短了文件的处理时间。NET代码，将正则表达式拆分为多个部分并并行执行
为什么Java处理这个正则表达式要快得多
我能做些什么来提高效率。处理这个正则表达式的净性能

干杯，
多伦

# 1 楼答案

我现在没有时间完成我的分析，但我会提供到目前为止的进展。这是重新格式化的正则表达式，这样您就可以真正阅读它了。我所做的唯一改变是在字符类中包装一些空格，以允许自由间隔模式。共有80个俘虏小组（Yipes！-其中大部分似乎没有必要）。这个表达式似乎与日期的各种形式相匹配。还有很多有待改进的地方：

private static pattern = @"
    # Match various forms of a Date.
      (                                     # Begin $1:
        (\D|^)                              # $2:
        (19|20|)\d\d                        # $3:
        ([- /.\\])                          # $4:
        (0[1-9]|1[012]|[1-9])               # $5:
        \4
        (0[1-9]|[12][0-9]|3[01]|[0-9])      # $6:
        [ ][ ]
        (\D|$)                              # $7:
      )                                     # End $1:
    | (                                     # Begin $8:
        (\D|^)                              # $9:
        (19|20|)\d\d                        # $10:
        ([- /.\\])                          # $11:
        (0[1-9]|[12][0-9]|3[01]|[0-9])      # $12:
        \11
        (0[1-9]|1[012]|[0-9])               # $13:
        [ ][ ]
        (\D|$)                              # $14:
      )                                     # End $8:
    | (                                     # Begin $15:
        (\D|^)                              # $16:
        (0[1-9]|1[012]|[0-9])               # $17:
        ([- /.\\])                          # $18:
        (0[1-9]|[12][0-9]|3[01]|[0-9])      # $19:
        \18
        (19|20|)\d\d                        # $20:
        (\D|$)                              # $21:
      )                                     # End $15:
    | (                                     # Begin $22:
        (\D|^)                              # $23:
        (0[1-9]|[12][0-9]|3[01]|[0-9])      # $24:
        ([- /.\\])                          # $25:
        (0[1-9]|1[012]|[0-9])               # $26:
        \25
        (19|20|)\d\d                        # $27:
        (\D|$)                              # $28:
      )                                     # End $22:
    | (                                     # Begin $29:
        (\D|^)                              # $30:
        (19|20|)\d\d                        # $31:
        (0[1-9]|1[012])                     # $32:
        (0[1-9]|[12][0-9]|3[01])            # $33:
        (\D|$)                              # $34:
      )                                     # End $29:
    | (                                     # Begin $35:
        (\D|^)                              # $36:
        (19|20|)\d\d                        # $37:
        (0[1-9]|[12][0-9]|3[01])            # $38:
        (0[1-9]|1[012])                     # $39:
        (\D|$)                              # $40:
      )                                     # End $35:
    | (                                     # Begin $41:
        (\D|^)                              # $42:
        (0[1-9]|1[012])                     # $43:
        (0[1-9]|[12][0-9]|3[01])            # $44:
        (19|20|)\d\d                        # $45:
        (\D|$)                              # $46:
      )                                     # End $41:
    | (                                     # Begin $47:
        (\D|^)                              # $48:
        (0[1-9]|[12][0-9]|3[01])            # $49:
        (0[1-9]|1[012])                     # $50:
        (19|20|)\d\d                        # $51:
        (\D|$)                              # $52:
      )                                     # End $47:
    | (                                     # Begin $53:
        ( ^                                 # Begin $54:
        | (?<!
            (\d[- /.\\\d])                  # $55:
          | \d
          )
        )                                   # End $54:
        (19|20|)\d\d                        # $56:
        ([- /.\\])                          # $57:
        (0[1-9]|1[012]|[1-9])               # $58:
        ([^- /.\\\d\w]|$|\s)                # $59:
      )                                     # End $53:
    | (                                     # Begin $60:
        ( ^                                 # Begin $61:
        | (?<!
            (\d[- /.\\\d])                  # $62:
          | \d
          )
        )                                   # End $61:
        (0[1-9]|1[012]|[1-9])               # $63:
        ([- /.\\])                          # $64:
        (19|20|)\d\d                        # $65:
        ([^- /.\\\d\w]|$|\s)                # $66:
      )                                     # End $60:
    | (                                     # Begin $67:
        ( ^                                 # Begin $68:
        | (?<!
            (\d[- /.\\\d])                  # $69:
          |\d
          )
        )                                   # End $68:
        (0[1-9]|1[012]|[1-9])               # $70:
        ([- /.\\])                          # $71:
        (0[1-9]|[12][0-9]|3[01])            # $72:
        ([^- /.\\\d\w]|$|\s))               # $73:
    | (                                     # Begin $74:
        ( ^                                 # Begin $75:
        | (?<!
            (\d[- /.\\\d])                  # $76:
          | \d
          )
        )                                   # End $75:
        (0[1-9]|[12][0-9]|3[01])            # $77:
        ([- /.\\])                          # $78:
        (0[1-9]|1[012]|[1-9])               # $79:
        ([^- /.\\\d\w]|$|\s)                # $80:
      )                                     # End $74:
    ";

当我有更多的时间时，我会用一些建议的改进来更新这个答案。同时，其他regex专家请随意使用这个改进的部分评论版本并使用它运行

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正则表达式在中的性能。NET vs Java

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