Is it really so slow to use LINQ for video games? And what if we compile our unity code with IL2CPP?
Using Unity's performance benchmark package, here are some tests to run.
LINQ is still remarkably slower than writing the code yourself. For critical performance code. Don't use LINQ.
| Function | Deviation | Standard deviation | Median | GC |
|---|---|---|---|---|
| Where - Divide by 3 No LINQ | 0.25 | 0.03 | 0.12 | 12 |
| Where - Divide by 3 LINQ Query | 0.18 | 0.02 | 0.11 | 13 |
| Where - Divide by 3 LINQ | 0.08 | 0.01 | 0.11 | 13 |
| Sum - No LINQ | 0.07 | 0.01 | 0.11 | 0 |
| Sum - LINQ | 0.30 | 0.06 | 0.19 | 1 |
| Select - Subtype No LINQ | 0.25 | 0.05 | 0.19 | 2 |
| Select - Subtype LINQ Query | 0.05 | 0.01 | 0.23 | 3 |
| Select - Subtype LINQ | 0.16 | 0.04 | 0.23 | 3 |
| Select - Add 1 No LINQ | 0.18 | 0.03 | 0.16 | 0 |
| Select - Add 1 LINQ Query | 0.06 | 0.01 | 0.22 | 3 |
| Select - Add 1 LINQ | 0.07 | 0.01 | 0.21 | 3 |
| OfType - Complex No LINQ | 0.07 | 0.03 | 0.37 | 0 |
| OfType - Complex No LINQ - Generic | 0.15 | 0.07 | 0.51 | 0 |
| OfType - Complex LINQ | 007 | 0.21 | 3.08 | 0 |
| OfType - Simple No LINQ | 0.14 | 0.04 | 0.26 | 12 |
| OfType - Simple No LINQ Query | 0.08 | 0.03 | 0.33 | 12 |
| OfType - Simple LINQ | 0.13 | 0.18 | 1.35 | 14 |
| Distinct - No LINQ Naive Prealloc | 0.02 | 17.96 | 830.90 | 2 |
| Distinct - No LINQ Naive No Prealloc | 0.02 | 20.24 | 830.24 | 14 |
| Distinct - No LINQ HashSet | 0.34 | 0.47 | 1.39 | 6 |
| Distinct - LINQ | 0.33 | 0.29 | 0.88 | 29 |
Open Unity, Open Window > General > Test Runner and Window > Analysis > Performance Test Report
In the test runner window, run all tests In the performance test report window, press refresh and investigate.
Simply create a new script and run it with the test runner.
Download the tool here https://github.com/Unity-Technologies/PerformanceBenchmarkReporter
Syntax:
dotnet .\UnityPerformanceBenchmarkReporter.dll --results=C:\Projects\IL2CPP-LINQ\Builds\results\results.xml --reportdirpath=C:\Projects\IL2CPP-LINQ\report
Note that the results.xml is not generated when running tests from the editor. To generate the results.xml file, run the tests from unity command line as follows:
"C:\Program Files\Unity\Hub\Editor\2019.1.14f1\Editor\Unity.exe" -runTests -batchMode -projectPath C:\Projects\IL2CPP-LINQ\ -scriptingbackend=il2cpp -testPlatform playmode -buildTarget Win -testResults C:\Projects\IL2CPP-LINQ\Builds\results\results.xml -logFile C:\Projects\IL2CPP-LINQ\Log.txt