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[Merged by Bors] - Optimize Iterator::count for event iterators #7582

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[Merged by Bors] - Optimize Iterator::count for event iterators #7582

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JoJoJet
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@JoJoJet JoJoJet commented Feb 9, 2023 •
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Objective

Related to #7530.

EventReader iterators currently use the default impl for .count(), which unnecessarily loops over all unread events.

Solution

Add specialized impls that mark the EventReader as consumed and return the number of unread events.

@JoJoJet JoJoJet added A-ECS Entities, components, systems, and events C-Performance A change motivated by improving speed, memory usage or compile times labels Feb 9, 2023
@alice-i-cecile alice-i-cecile added the S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it label Feb 9, 2023
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mockersf commented Feb 9, 2023 •
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Those iterators also implement ExactSizedIterator which adds a len() method that is optimised. Implementing them that way would mean that the doc for those trait methods would be wrong.

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JoJoJet commented Feb 9, 2023

Implementing them that way would mean that the doc for those trait methods would be wrong.

What do you mean by this?

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mockersf commented Feb 9, 2023

the doc for the trait methods is https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.count which specifically mention calling all the next

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JoJoJet commented Feb 9, 2023 •
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Correct me if I'm wrong, but there is no observable difference between repeatedly calling next and the approach used in this PR. It's the same exact behavior, just more efficient.

@alice-i-cecile alice-i-cecile removed the S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it label Feb 9, 2023
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Correct me if I'm wrong, but there is no observable difference between repeatedly calling next and the approach used in this PR. It's the same exact behavior, just more efficient.

You're right. Let's hope no one rely on something being not the most efficient 😄

@alice-i-cecile alice-i-cecile added the S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it label Feb 10, 2023
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alice-i-cecile approved these changes Feb 13, 2023
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Merging as trivial now that we've discussed it.

bors r+

bors bot pushed a commit that referenced this pull request Feb 13, 2023
@JoJoJet
Optimize Iterator::count for event iterators (#7582)
10d0336 
# Objective

Related to #7530.

`EventReader` iterators currently use the default impl for `.count()`, which unnecessarily loops over all unread events.

# Solution

Add specialized impls that mark the `EventReader` as consumed and return the number of unread events.
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bors bot commented Feb 13, 2023

Pull request successfully merged into main.

Build succeeded:

@bors bors bot changed the title Optimize Iterator::count for event iterators [Merged by Bors] - Optimize Iterator::count for event iterators Feb 13, 2023
@bors bors bot closed this Feb 13, 2023
myreprise1 pushed a commit to myreprise1/bevy that referenced this pull request Feb 14, 2023
@JoJoJet @myreprise1
Optimize Iterator::count for event iterators (bevyengine#7582)
73f4414 
# Objective

Related to bevyengine#7530.

`EventReader` iterators currently use the default impl for `.count()`, which unnecessarily loops over all unread events.

# Solution

Add specialized impls that mark the `EventReader` as consumed and return the number of unread events.
@JoJoJet JoJoJet deleted the optimize-event-count branch February 14, 2023 00:53
@JoJoJet JoJoJet mentioned this pull request Feb 14, 2023
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myreprise1 pushed a commit to myreprise1/bevy that referenced this pull request Feb 15, 2023
@JoJoJet @myreprise1
Optimize Iterator::count for event iterators (bevyengine#7582)
b0b8e55 
# Objective

Related to bevyengine#7530.

`EventReader` iterators currently use the default impl for `.count()`, which unnecessarily loops over all unread events.

# Solution

Add specialized impls that mark the `EventReader` as consumed and return the number of unread events.
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