.NET Span<T> better performance
May 12, 2018 · 2 min read
Span<T> is a new type which will be available on .NET Core 2.1.
To simplify it, you may think at it like a Value Type array
which can be slice into sub unit without memory allocation.
On the following section, I would like to present few benchmarks and code samples.
The benchmark compare the performance of slicing Array using:
- Array Copy
- Span<T>
- unsafe pointer
The benchmarks available at GitHub (it’s using BenchmarkDotNet).
All benchmarks are using the following array:
public int[] Data = Enumerable.Range(0, 10_000_000).ToArray();The classic array manipulation using is:
The Span<T> is using:
The Pointer is using:
The results was:
Method |Mean |Scaled |Rank |Allocated |
------- |------------:|------:|------:|----------:|
Array | 4,966.5 us | 1.00 | 3 | 4032 B |
Span | 162.9 us | 0.03 | 1 | 0 B |
Pointer | 175.3 us | 0.04 | 2 | 0 B |Some interesting facts on Span<T>:
- Add System.Memory NuGet in order you get reference to it.
- It cannot be allocate on the Heap,
therefore, cannot be member of a class. - It can be member of a ref struct.
- It shine when you have to do string manipulations like SubString
for example:
“AbCD”.AsSpan() returns ReadOnlySpan<char>
— — — — — — — — — — — — — — — — — — — — — — —
this means that you can use “ABCD”.AsSpan().Slice(2,1)
instead of “ABCD”.Substring(2,1).
You can read more about it in Stephen Toub’s Paper.
