From: merch-redmine@...
Date: 2021-02-13T07:49:46+00:00
Subject: [ruby-core:102476] [Ruby master Misc#15925] Speed up SortedSet#min,	#max, #sum etc.?

Issue #15925 has been updated by jeremyevans0 (Jeremy Evans).

Status changed from Assigned to Closed

SortedSet is no longer part of stdlib, so this can be closed.

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Misc #15925: Speed up SortedSet#min, #max, #sum etc.?
https://bugs.ruby-lang.org/issues/15925#change-90365

* Author: janosch-x (Janosch M�ller)
* Status: Closed
* Priority: Normal
* Assignee: knu (Akinori MUSHA)
----------------------------------------
this issue is somewhat similar to https://bugs.ruby-lang.org/issues/15807

current situation, using the example of `SortedSet#min` (without `rbtree`):

- `SortedSet#min` calls `Enumerable#min`
- `Enumerable#min` calls `SortedSet#each`
- `SortedSet#each` calls `SortedSet#to_a`
- `#to_a` returns an `Array` which is guaranteed to be sorted
- `Enumerable#min` wastefully goes through this whole `Array` anyway

so complexity can be reduced from O(n) to O(1) for `#min`/`#max`/`#minmax`.

other methods may be sped up by delegating to faster implementations on `Array`.

for instance, `SortedSet.new(1..1000).to_a.sum` is an order of magnitude faster than `SortedSet.new(1..1000).sum`.

suggestion:

```
class SortedSet < Set
  # [ ... ]
  # non-rbtree case
  # [ ... ]

  def min
    to_a.first
  end

  def max
    to_a.last
  end

  def minmax
    [min, max]
  end

  def sum
    to_a.sum
  end

  # maybe more?
end
```

---Files--------------------------------
sorted-set-min-max-sum.patch (1.85 KB)


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