Add `count(where:)` and tests #16099

khanlou · 2018-04-23T14:49:08Z

This pull request is a reference implementation and tests for the count(where:) function on Sequence. The relevant pitch thread can be found here.

Several notes:

There's currently a failing diagnostic test:

// <rdar://problem/21080030> Bad diagnostic for invalid method call in boolean expression: (_, ExpressibleByIntegerLiteral)' is not convertible to 'ExpressibleByIntegerLiteral
func rdar21080030() {
  var s = "Hello"
  if s.count() == 0 {} // expected-error{{cannot call value of non-function type 'Int'}}{{13-15=}}
}

This makes sense, because count is now a property and a function. Not sure what the recommended approach is here: do we delete this test? Do we change the expected error to "wrong number of parameters"?

I didn't include count(of:) where Element is Equatable, but I can, depending on what the temperature of the review is. If we do add count(of:), I think we probably also want to add specializations for ranges, sets, etc.
count(of:) also might need special consideration for NSCountedSet.

lattner · 2018-08-15T22:15:48Z

@swift-ci please test

lattner · 2018-08-15T22:16:16Z

This proposal has been accepted, please merge it when ready. Thank you for the contribution @khanlou !

khanlou · 2018-08-15T22:25:04Z

does it have merge conflicts? (there's no way to for me to see)

lattner · 2018-08-16T00:43:41Z

Seems like it merges fine. @airspeedswift, can you nominate someone to code review and merge this? Thanks.

airspeedswift

Tests look good, but could you add a benchmark as well? Maybe one on String or Set for some combined coverage.

airspeedswift · 2018-08-16T03:29:17Z

stdlib/public/core/SequenceAlgorithms.swift

+  public func count(
+    where predicate: (Element) throws -> Bool
+  ) rethrows -> Int {
+    var count = 0


Any reason to not use reduce here?

I think using a reduce is needlessly complicated both in terms of abstraction and in terms of code readability, which is why I went with the for loop. If you feel strongly, I can switch it to a reduce.

I disagree. This kind of calculation is exactly what reduce is for. It states declaratively what the code does instead of writing an open-coded for loop, so improves readability. It's also important that the code in the std lib encourage the practice of using map/reduce/filter where appropriate.

(it does bug me you have to write try twice with reduce, tho)

Hey, I know I'm very late to this but just now came across this proposal, I just have a question and my apologies if it's a dumb one, but wouldn't the below make more sense:

@inlinable public func count<T: Sequence>(where predicate: (Element) throws -> Bool) rethrows -> Int where T: Sequence, T.Element == Element, T: AnyObject { var count = 0 for element in self { if try predicate(element) { count += 1 } } return count }

The method is explicitly constrained to Sequence types to avoid ambiguity with Collection.count, which should help reduce the type checker's workload and resolve the performance issue.

The generic constraint T: AnyObject is added to restrict the method usage and aid the compiler in resolving type ambiguities more efficiently, although this might need to be adjusted based on the specific requirements and context.

airspeedswift · 2018-08-16T03:35:38Z

re the diagnostic test - you could replace with underestimatedCount. But seems like it isn’t failing any more?

airspeedswift · 2018-08-16T03:36:46Z

@natecook1000 any feedback on the doc comment?

tkremenek · 2018-08-22T16:38:35Z

@swift-ci test

tkremenek · 2018-08-22T16:38:42Z

Anything left to do here?

swift-ci · 2018-08-22T16:39:05Z

Build failed
Swift Test OS X Platform
Git Sha - 25b2fd8

swift-ci · 2018-08-22T16:41:15Z

Build failed
Swift Test Linux Platform
Git Sha - 25b2fd8

khanlou · 2018-08-22T16:53:25Z

@tkremenek Ben asked for a performance test, but I don't know how to add that yet, so I've been putting it off.

khanlou · 2018-08-25T03:51:42Z

Is there any way for me to see why the build failed? I'm getting a 404.

airspeedswift · 2018-08-25T04:43:36Z

Those aren’t real failures, you get them when you kick off a rerun of the tests sometimes. The tests then ran and passed.

khanlou · 2018-09-06T21:16:47Z

I got help from @natecook1000 and am working on the benchmark today and tomorrow. Hopefully will have something soon.

khanlou · 2018-09-07T13:37:48Z

Can someone kick off a benchmark run to make sure everything is working right?

natecook1000 · 2018-09-07T16:15:58Z

@swift-ci Please smoke benchmark

natecook1000 · 2018-09-07T16:16:44Z

@swift-ci Please smoke test

natecook1000 · 2018-09-07T16:24:36Z

@swift-ci Please smoke benchmark

swift-ci · 2018-09-07T17:03:08Z

Build comment file:

Performance: -O

TEST	MIN	MAX	MEAN	MAX_RSS
Added
CountAlgoRange	2859	2940	2886	—
CountAlgoString	3445	3676	3523	—

Performance: -Osize

TEST	MIN	MAX	MEAN	MAX_RSS
Added
CountAlgoRange	5716	5846	5760	—
CountAlgoString	3437	3569	3482	—

Performance: -Onone

TEST	MIN	MAX	MEAN	MAX_RSS
Added
CountAlgoRange	2564333	2565523	2564903	—
CountAlgoString	4843	4975	4888	—

How to read the data

The tables contain differences in performance which are larger than 8% and differences in code size which are larger than 1%.

If you see any unexpected regressions, you should consider fixing the regressions before you merge the PR.

Noise: Sometimes the performance results (not code size!) contain false alarms. Unexpected regressions which are marked with '(?)' are probably noise. If you see regressions which you cannot explain you can try to run the benchmarks again. If regressions still show up, please consult with the performance team (@eeckstein).

Hardware Overview

  Model Name: Mac Pro
  Model Identifier: MacPro6,1
  Processor Name: 12-Core Intel Xeon E5
  Processor Speed: 2.7 GHz
  Number of Processors: 1
  Total Number of Cores: 12
  L2 Cache (per Core): 256 KB
  L3 Cache: 30 MB
  Memory: 64 GB

natecook1000 · 2018-09-07T17:07:42Z

Quite a difference between optimized and unoptimized for the range!

khanlou · 2018-09-12T16:09:02Z

What should we do about the range benchmark? I'm assuming 40 minutes is too long to include in the suite

natecook1000 · 2018-09-12T22:21:32Z

@swift-ci Please smoke benchmark

swift-ci · 2018-09-12T22:49:06Z

Build comment file:

Performance: -O

TEST	MIN	MAX	MEAN	MAX_RSS
Added
CountAlgoArray	575	585	578	—
CountAlgoString	3429	3612	3490	—

Performance: -Osize

TEST	MIN	MAX	MEAN	MAX_RSS
Added
CountAlgoArray	576	576	576	—
CountAlgoString	3425	3697	3540	—

Performance: -Onone

TEST	MIN	MAX	MEAN	MAX_RSS
Added
CountAlgoArray	144507	170970	153367	—
CountAlgoString	4755	4858	4803	—

How to read the data

The tables contain differences in performance which are larger than 8% and differences in code size which are larger than 1%.

If you see any unexpected regressions, you should consider fixing the regressions before you merge the PR.

Noise: Sometimes the performance results (not code size!) contain false alarms. Unexpected regressions which are marked with '(?)' are probably noise. If you see regressions which you cannot explain you can try to run the benchmarks again. If regressions still show up, please consult with the performance team (@eeckstein).

Hardware Overview

  Model Name: Mac Pro
  Model Identifier: MacPro6,1
  Processor Name: 12-Core Intel Xeon E5
  Processor Speed: 2.7 GHz
  Number of Processors: 1
  Total Number of Cores: 12
  L2 Cache (per Core): 256 KB
  L3 Cache: 30 MB
  Memory: 64 GB

natecook1000 · 2018-09-13T00:43:27Z

@swift-ci Please smoke test

khanlou · 2018-09-13T16:00:12Z

Does this PR need anything else?

airspeedswift · 2018-09-13T18:33:32Z

I raised https://bugs.swift.org/browse/SR-8742 for the weird Range benchmark thing.

@natecook1000

* add count(where:) and tests * Revise count(where:) documentation * Remove errant word in abstract * add a benchmark for ranges and strings with help from @natecook1000 * update benchmark to use Array instead of Range

Done here swiftlang/swift#16099

add count(where:) and tests

25b2fd8

khanlou mentioned this pull request Apr 23, 2018

Add a proposal for count(where:) swiftlang/swift-evolution#840

Merged

natecook1000 added the swift evolution pending discussion Flag → feature: A feature that has a Swift evolution proposal currently in review label Apr 23, 2018

lattner added swift evolution approved Flag → feature: A feature that was approved through the Swift evolution process and removed swift evolution pending discussion Flag → feature: A feature that has a Swift evolution proposal currently in review labels Aug 15, 2018

airspeedswift self-requested a review August 16, 2018 03:28

airspeedswift reviewed Aug 16, 2018

View reviewed changes

natecook1000 added 2 commits August 16, 2018 03:38

Revise count(where:) documentation

58569cf

Remove errant word in abstract

3227193

add a benchmark for ranges and strings with help from @natecook1000

0bdcb82

update benchmark to use Array instead of Range

70d2929

natecook1000 merged commit 5736cac into swiftlang:master Sep 13, 2018

khanlou deleted the add-count-where branch September 13, 2018 17:40

mackoj added a commit to mackoj/swift-evolution that referenced this pull request Jan 10, 2020

Update 0220-count-where.md

26cfb4c

Done here swiftlang/swift#16099

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Add `count(where:)` and tests #16099

Add `count(where:)` and tests #16099

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Add count(where:) and tests #16099

Add count(where:) and tests #16099

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Build comment file:

Performance: -O

Performance: -Osize

Performance: -Onone

natecook1000 commented Sep 7, 2018

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swift-ci commented Sep 12, 2018

Build comment file:

Performance: -O

Performance: -Osize

Performance: -Onone

natecook1000 commented Sep 13, 2018

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airspeedswift commented Sep 13, 2018

Add `count(where:)` and tests #16099

Add `count(where:)` and tests #16099

khanlou commented Apr 23, 2018 •

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