[#99868] [Ruby master Bug#17144] Tempfile.open { ... } does not unlink the file — eregontp@...
Issue #17144 has been reported by Eregon (Benoit Daloze).
15 messages
2020/09/03
[ruby-core:100242] [Ruby master Feature#17206] Introduce new Regexp option to avoid global MatchData allocations
From:
eregontp@...
Date:
2020-09-30 18:18:26 UTC
List:
ruby-core #100242
Issue #17206 has been updated by Eregon (Benoit Daloze).
IMHO hardcoding such knowledge in the pattern feels wrong (vs in the matching method like `Regexp#match?` which is fine).
It seems to me that it could cause confusing bugs, e.g. when using `/f` in the `case` above if a `when` clause starts to use one of the `$~`-derived variables.
Then it would unexpectedly always be `nil`, causing a potentially very subtle bug.
I have a hard time to believe that allocating the MatchData is so expensive.
If that's the case, then there must be a lot of optimization potential for faster allocation of MatchData in CRuby.
What I think rather is this is due to having to set $~ in the caller, and maybe to compute group offsets.
I think it would be worth investigating more in details where does the performance overhead from `$~` & friends come from in CRuby.
----------------------------------------
Feature #17206: Introduce new Regexp option to avoid global MatchData allocations
https://bugs.ruby-lang.org/issues/17206#change-87829
* Author: fatkodima (Dima Fatko)
* Status: Open
* Priority: Normal
----------------------------------------
Originates from https://bugs.ruby-lang.org/issues/17030
When this option is specified, ruby will not create global `MatchData` objects, when not explicitly needed by the method.
If the new option is named `f`, we can write as `/o/f`, and `grep(/o/f)` is faster than `grep(/o/)`.
This speeds up not only `grep`, but also `all?`, `any?`, `case` and so on.
Many people have written code like this:
```ruby
IO.foreach("foo.txt") do |line|
case line
when /^#/
# do nothing
when /^(\d+)/
# using $1
when /xxx/
# using $&
when /yyy/
# not using $&
else
# ...
end
end
```
This is slow, because of the above mentioned problem.
Replacing `/^#/` with `/^#/f`, and `/yyy/` with `/yyy/f` will make it faster.
Some benchmarks - https://bugs.ruby-lang.org/issues/17030#note-9 which show `2.5x` to `5x` speedup.
PR: https://github.com/ruby/ruby/pull/3455
--
https://bugs.ruby-lang.org/
Unsubscribe: <mailto:[email protected]?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>