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I understand unsafe code is more appropriate to access things like the Windows API and do unsafe type castings than to write more performant code, but I would like to ask you if you have ever noticed any significant performance improvement in real-world applications by using it when compared to safe c# code.
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The specification implies unsafe code is inherently faster with pointers.
Unsafe code in general is a keyword that denotes a code section that is not handled by the Common Language Runtime(CLR). Pointers are not supported by default in C# but unsafe keyword allows the use of the pointer variables.
Create a file in your <Project Path>/Assets directory and name it smcs. rsp then put -unsafe inside that file. Save and close that file. Close and reopen Visual Studio and Unity Editor.
Unsafe code in C# is the part of the program that runs outside the control of the Common Language Runtime (CLR) of the . NET frameworks. The CLR is responsible for all of the background tasks that the programmer doesn't have to worry about like memory allocation and release, managing stack etc.
Some Performance Measurements
The performance benefits are not as great as you might think.
I did some performance measurements of normal managed array access versus unsafe pointers in C#.
Results from a build run outside of Visual Studio 2010, .NET 4, using an Any CPU | Release build on the following PC specification: x64-based PC, 1 quad-core processor. Intel64 Family 6 Model 23 Stepping 10 GenuineIntel ~2833 Mhz.
Linear array access 00:00:07.1053664 for Normal 00:00:07.1197401 for Unsafe *(p + i) Linear array access - with pointer increment 00:00:07.1174493 for Normal 00:00:10.0015947 for Unsafe (*p++) Random array access 00:00:42.5559436 for Normal 00:00:40.5632554 for Unsafe Random array access using Parallel.For(), with 4 processors 00:00:10.6896303 for Normal 00:00:10.1858376 for Unsafe
Note that the unsafe *(p++) idiom actually ran slower. My guess this broke a compiler optimization that was combining the loop variable and the (compiler generated) pointer access in the safe version.
Source code available on github.
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