From: ruby-core@...
Date: 2018-11-03T15:51:48+00:00
Subject: [ruby-core:89697] [Ruby trunk Feature#15281] Speed up Set#intersect	with size check.

Issue #15281 has been updated by marcandre (Marc-Andre Lafortune).


Thanks for the patch.

Sadly, I don't think we can do that as `Set`s are ordered. That optimization would change the order of the resulting `Set` in some cases.

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Feature #15281: Speed up Set#intersect with size check.
https://bugs.ruby-lang.org/issues/15281#change-74740

* Author: RGBD (Oleg Zubchenko)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
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Current implementation computes set intersection s1 & s2 in O(s2.size) time.
It can be reduced to O([s1.size, s2.size].min) time.

Additional speedup comes from using #each instead of #do_with_enum.

See files attached for benchmarks.

[Pull Request](https://github.com/ruby/ruby/pull/2003)

P.S. using benchmark-ips gem

---Files--------------------------------
intersect.rb (1.91 KB)
intersect_standalone.rb (671 Bytes)
benchmark_results.txt (3.68 KB)


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