Avoid unnecessary allocations in PriorityQueue.EnqueueRange

[eiriktsarpalis]

While investigating the performance regression reported in #50052 I discovered an issue in the implementation of PriorityQueue.EnqueueRange where the call to EnumerableHelpers.ToArray will often result in unnecessary allocations of buffers.

Performance

Running the HeapSort benchmark from dotnet/performance:

main

Method	Size	Mean	Error	StdDev	Median	Min	Max	Gen 0	Gen 1	Gen 2	Allocated
HeapSort	10	169.1 ns	0.84 ns	0.70 ns	168.9 ns	168.4 ns	170.8 ns	0.0100	-	-	104 B
HeapSort	100	2,639.9 ns	7.44 ns	6.60 ns	2,638.9 ns	2,626.4 ns	2,650.1 ns	0.0744	-	-	824 B
HeapSort	1000	71,286.5 ns	271.46 ns	253.92 ns	71,274.5 ns	70,843.3 ns	71,722.1 ns	0.5605	-	-	8,024 B

PR branch

Method	Size	Mean	Error	StdDev	Median	Min	Max	Gen 0	Gen 1	Gen 2	Allocated
HeapSort	10	151.8 ns	0.79 ns	0.62 ns	151.8 ns	150.7 ns	153.0 ns	-	-	-	-
HeapSort	100	2,582.6 ns	39.87 ns	33.30 ns	2,583.8 ns	2,515.2 ns	2,630.6 ns	-	-	-	-
HeapSort	1000	67,370.4 ns	222.44 ns	185.75 ns	67,386.2 ns	66,978.4 ns	67,707.7 ns	-	-	-	-

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Issue Details

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While investigating the performance regression reported in #50052 I discovered an issue in the implementation of PriorityQueue.EnqueueRange where the call to EnumerableHelpers.ToArray will often result in unnecessary allocations of buffers.

Performance

Running the HeapSort benchmark from dotnet/performance:

main

Method	Size	Mean	Error	StdDev	Median	Min	Max	Gen 0	Gen 1	Gen 2	Allocated
HeapSort	10	169.1 ns	0.84 ns	0.70 ns	168.9 ns	168.4 ns	170.8 ns	0.0100	-	-	104 B
HeapSort	100	2,639.9 ns	7.44 ns	6.60 ns	2,638.9 ns	2,626.4 ns	2,650.1 ns	0.0744	-	-	824 B
HeapSort	1000	71,286.5 ns	271.46 ns	253.92 ns	71,274.5 ns	70,843.3 ns	71,722.1 ns	0.5605	-	-	8,024 B

PR branch

Method	Size	Mean	Error	StdDev	Median	Min	Max	Gen 0	Gen 1	Gen 2	Allocated
HeapSort	10	151.8 ns	0.79 ns	0.62 ns	151.8 ns	150.7 ns	153.0 ns	-	-	-	-
HeapSort	100	2,582.6 ns	39.87 ns	33.30 ns	2,583.8 ns	2,515.2 ns	2,630.6 ns	-	-	-	-
HeapSort	1000	67,370.4 ns	222.44 ns	185.75 ns	67,386.2 ns	66,978.4 ns	67,707.7 ns	-	-	-	-

Author:	eiriktsarpalis
Assignees:	eiriktsarpalis
Labels:	area-System.Collections
Milestone:	6.0.0