dotnet/runtime

Indexer.Set of List is much slower than Array

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#29,091 opened on Mar 27, 2019

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area-CodeGen-coreclrhelp wantedtenet-performance

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Description

How to run the benchmarks:

git clone https://github.com/dotnet/performance.git
# if you have .NET Core 3.0 installed
dotnet run -c Release -f netcoreapp3.0 -p .\performance\src\benchmarks\micro\MicroBenchmarks.csproj --filter *IndexerSet*.List *IndexerSet*.Array --join
# if you don't have .NET Core 3.0 installed
py .\performance\scripts\benchmarks_ci.py -f netcoreapp3.0 --filter *IndexerSet*.List *IndexerSet*.Array --bdn-arguments="--join true"
Type Method Size Mean
IndexerSet<Int32> Array 512 198.7 ns
IndexerSet<String> Array 512 199.5 ns
IndexerSetReverse<Int32> Array 512 215.6 ns
IndexerSetReverse<String> Array 512 219.7 ns
IndexerSet<Int32> List 512 986.2 ns
IndexerSet<String> List 512 930.1 ns
IndexerSetReverse<Int32> List 512 947.0 ns
IndexerSetReverse<String> List 512 817.4 ns

Full docs for the new benchmarking workflow: https://github.com/dotnet/performance/blob/master/docs/benchmarking-workflow-corefx.md

category:performance theme:benchmarks

Contributor guide

Research direction
Compare the JIT generated code for List<T> indexer set and array indexer set. Check for differences in bounds checking elimination and inlining.
Tech stack
csharp
Domain
performance
Issue type
Performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
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1-3 hours
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Clear
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45