[cutler]

Much as I would love to believe Ruby 3.0 delivers some kind of speed bump my simple test of doing what Ruby supposedly does best - parsing a log file with a regex - shows Ruby 16% slower than the Python equivalent.

  Ruby
  puts IO.foreach('logs1.txt').grep /\b\w{15}\b/

  Python
  from re import compile

  with open('logs1.txt', 'r') as fh:
      regex = compile(r'\b\w{15}\b')
      for line in fh:
          if regex.search(line): print(line, end='')

On my MacBook Pro (2013) running Catalina Ruby averaged 1.49 secs and Python 1.27 secs. The file `logs1.txt` is a 20Mb Apache log file. Pre-compilation with:

   reg = Regex.compile /\b\w{15}\b/
   puts IO.foreach('logs1.txt').grep reg

... slowed Ruby down to 1.57 secs.

Using --jit didn't change Ruby's overall time but considering it adds 700ms to Ruby's startup time execution time was faster.

[karmakaze]

The programs aren't doing the same things. The Ruby one seems to buffer the matches into a huge string then print. Don't know how different it would be but better to compare apples.

[riffraff]

Probably the equivalent thing to test would be

      regexp = /\b\w{15}\b/
      IO.foreach('logs1.txt') do |line|
        puts line if regexp.match?(line)
      end

I imagine this will in both cases mostly be testing the computer's IO.

Regexp.compile doesn't do anything substantially different from Regexp.new or a literal (i.e. it doesn't optimize the regular expression or something) so I think the difference is just random fluctuations.

[cutler]

IO.foreach without a block returns an enumerator.

[cutler]

You may be right. This version:

    IO.foreach('logs1.txt') {|x| puts x if /\b\w{15}\b/.match? x }

... runs in 1.3 secs, ie. same time as Python. Still, I exepcted Ruby 3x3 to beat standard Python.

[TylerE]

That's not really surprising since regex in most languages is PCRE and not really indicative of actual interpreter performance.

[cutler]

If that's the case why is Ruby slower?

[byroot]

Your Ruby snippet is slower for two reasons:

  - IO.foreach is lazy, but then you call `Array#grep` on it which allocate a huge Array
  - `grep` populate the "last_match" object, `String#match?` is much faster.

Try rifraf's snippet: https://news.ycombinator.com/item?id=24597067, it should be as fast as Python.

[TylerE]

Because what you’re really measuring is something like how well the block size the interpreter uses for IO matches the underlying os/hardware

[cutler]

If they are both doing similar things and one is faster that's still significant. So Python's i/o is faster than Ruby's.

[Ecco]

But it’s a super easy to read one-liner in Ruby!