IEnumerable<T> does not allow for modification during iteration. But if you want to support
that functionality on custom generic data structures, is it faster to modify and return the
value (example: using Func<T, T>), or is it faster to use ref parameters? That is the goal
of this benchmark.
Conclusion from results below:
Using ref parameters are simply less efficient for passing ints.
BenchmarkDotNet=v0.13.0, OS=Windows 10.0.19041.985 (2004/May2020Update/20H1)
Intel Core i5-8400 CPU 2.80GHz (Coffee Lake), 1 CPU, 6 logical and 6 physical cores
.NET SDK=5.0.301
[Host] : .NET 5.0.7 (5.0.721.25508), X64 RyuJIT
Job-YFVYXE : .NET 5.0.7 (5.0.721.25508), X64 RyuJIT
InvocationCount=1 UnrollFactor=1
| Method | N | Mean | Error | StdDev | Median |
|---|---|---|---|---|---|
| Control | 10 | 75.26 ns | 17.959 ns | 52.104 ns | 100.0 ns |
| DelegateReturn | 10 | 188.10 ns | 12.127 ns | 32.579 ns | 200.0 ns |
| DelegateRefParam | 10 | 242.05 ns | 21.827 ns | 60.118 ns | 200.0 ns |
| StructGenericReturn | 10 | 84.62 ns | 14.068 ns | 36.314 ns | 100.0 ns |
| StructGenericRefParam | 10 | 100.00 ns | 0.000 ns | 0.000 ns | 100.0 ns |
| FunctionPointer | 10 | 100.00 ns | 0.000 ns | 0.000 ns | 100.0 ns |
| FunctionPointerRefParam | 10 | 137.37 ns | 17.281 ns | 50.681 ns | 100.0 ns |
| Control | 100 | 142.86 ns | 20.296 ns | 59.204 ns | 100.0 ns |
| DelegateReturn | 100 | 373.33 ns | 15.953 ns | 44.469 ns | 400.0 ns |
| DelegateRefParam | 100 | 396.77 ns | 11.761 ns | 17.961 ns | 400.0 ns |
| StructGenericReturn | 100 | 139.58 ns | 17.765 ns | 51.256 ns | 100.0 ns |
| StructGenericRefParam | 100 | 173.00 ns | 18.579 ns | 54.781 ns | 200.0 ns |
| FunctionPointer | 100 | 296.00 ns | 9.799 ns | 19.795 ns | 300.0 ns |
| FunctionPointerRefParam | 100 | 292.21 ns | 10.525 ns | 26.981 ns | 300.0 ns |
| Control | 1000 | 714.61 ns | 25.835 ns | 71.590 ns | 700.0 ns |
| DelegateReturn | 1000 | 2,111.76 ns | 45.134 ns | 72.883 ns | 2,100.0 ns |
| DelegateRefParam | 1000 | 2,151.72 ns | 39.194 ns | 57.450 ns | 2,100.0 ns |
| StructGenericReturn | 1000 | 630.00 ns | 18.197 ns | 50.725 ns | 600.0 ns |
| StructGenericRefParam | 1000 | 670.73 ns | 18.252 ns | 48.401 ns | 700.0 ns |
| FunctionPointer | 1000 | 1,968.42 ns | 42.966 ns | 47.757 ns | 2,000.0 ns |
| FunctionPointerRefParam | 1000 | 1,992.31 ns | 36.682 ns | 94.689 ns | 1,950.0 ns |
| Control | 10000 | 6,061.54 ns | 60.640 ns | 50.637 ns | 6,100.0 ns |
| DelegateReturn | 10000 | 19,041.67 ns | 85.632 ns | 66.856 ns | 19,000.0 ns |
| DelegateRefParam | 10000 | 19,642.86 ns | 186.226 ns | 165.084 ns | 19,600.0 ns |
| StructGenericReturn | 10000 | 5,473.91 ns | 109.817 ns | 138.883 ns | 5,400.0 ns |
| StructGenericRefParam | 10000 | 6,507.69 ns | 103.266 ns | 86.232 ns | 6,500.0 ns |
| FunctionPointer | 10000 | 18,769.23 ns | 57.528 ns | 48.038 ns | 18,800.0 ns |
| FunctionPointerRefParam | 10000 | 18,830.77 ns | 157.547 ns | 131.559 ns | 18,800.0 ns |
| Control | 100000 | 60,658.82 ns | 850.069 ns | 1,372.703 ns | 60,150.0 ns |
| DelegateReturn | 100000 | 191,573.33 ns | 3,422.537 ns | 3,201.443 ns | 191,000.0 ns |
| DelegateRefParam | 100000 | 195,771.43 ns | 2,473.219 ns | 2,192.445 ns | 194,500.0 ns |
| StructGenericReturn | 100000 | 53,325.00 ns | 1,007.244 ns | 786.390 ns | 53,000.0 ns |
| StructGenericRefParam | 100000 | 63,509.52 ns | 1,174.654 ns | 2,147.921 ns | 63,500.0 ns |
| FunctionPointer | 100000 | 186,592.31 ns | 1,296.685 ns | 1,082.791 ns | 186,100.0 ns |
| FunctionPointerRefParam | 100000 | 187,740.00 ns | 1,850.697 ns | 1,731.143 ns | 186,900.0 ns |