LruCache faster snapshot

[Scooletz]

This PR changes LruCache snapshot into an array. As the snapshot is used only in pruning and requires no Dictionary interface, it can be provided with an array that saves on comparisons, hashing and more.

Changes

• LruCache.Clone is array returning

Types of changes

What types of changes does your code introduce?

• Bugfix (a non-breaking change that fixes an issue)
• New feature (a non-breaking change that adds functionality)
• Breaking change (a change that causes existing functionality not to work as expected)
• Optimization
• Refactoring
• Documentation update
• Build-related changes
• Other: Description

Testing

Requires testing

• Yes - running a pruning would not hurt a lot
• No

If yes, did you write tests?

• Yes
• No

[OneOnlyMechanic]

@Scooletz just came across this PR. It may be interesting to consider ValueTuple instead of KeyValuePair here. I believe ValueTuple in general is slightly faster.

[Scooletz]

@OneOnlyMechanic What do you mean by the following?

ValueTuple in general is slightly faster

Can you elaborate, provide a benchmark or a link to some article about it? The PR was changing much heavier heavy dictionary that was not needed to a plain an array.

[OneOnlyMechanic]

@OneOnlyMechanic What do you mean by the following?

ValueTuple in general is slightly faster

Can you elaborate, provide a benchmark or a link to some article about it? The PR was changing much heavier heavy dictionary that was not needed to a plain an array.

Agreed that changing from ToDictionary to an Array of KeyValuePair should give a performance boost.

As for value tuple, see the benchmark section here: https://www.dotnetperls.com/tuple
One caveat is the benchmark uses tuple of strings. It may be interesting to rerun the test with different type, such as byte[] to confirm.

[Scooletz]

Interesting. I run it with Sharplab and the resulting asm is exactly the same for KV and tuple. Won't be pursuing this.

[OneOnlyMechanic]

Nice to know the asm is the same!
BTW, I did some test. Your change to using Array compared to ToDictionary is about 8 times faster.