From: merch-redmine@...
Date: 2019-06-17T21:29:31+00:00
Subject: [ruby-core:93210] [Ruby trunk Misc#15925] Speed up SortedSet#min,	#max, #sum etc.?

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

Assignee set to knu (Akinori MUSHA)
Status changed from Open to Assigned
File sorted-set-min-max-sum.patch added

Your recommended implementation greatly improves performance.  From the benchmark in the attached patch:


```
Calculating -------------------------------------
                     ../ruby2/run_ruby    run_ruby
                 min            4.811k      1.166M i/s -     14.501k times in 3.014412s 0.012441s
                 max            4.761k      1.215M i/s -     14.187k times in 2.979777s 0.011680s
              minmax            4.530k    321.515k i/s -     13.505k times in 2.980916s 0.042004s
                 sum            5.924k    113.139k i/s -     17.646k times in 2.978920s 0.155968s

Comparison:
                              min
            run_ruby:   1165552.1 i/s
   ../ruby2/run_ruby:      4810.6 i/s - 242.29x  slower

                              max
            run_ruby:   1214686.2 i/s
   ../ruby2/run_ruby:      4761.1 i/s - 255.13x  slower

                           minmax
            run_ruby:    321514.7 i/s
   ../ruby2/run_ruby:      4530.5 i/s - 70.97x  slower

                              sum
            run_ruby:    113138.6 i/s
   ../ruby2/run_ruby:      5923.6 i/s - 19.10x  slower

```

----------------------------------------
Misc #15925: Speed up SortedSet#min, #max, #sum etc.?
https://bugs.ruby-lang.org/issues/15925#change-78656

* Author: janosch-x (Janosch M�ller)
* Status: Assigned
* 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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