There are many ways to remove spaces or other characters in a string - there are just very big differences in terms of performance and efficiency.
Benchmark
As part of my Sustainable Code Repository , I have created various code snippets to simulate everyday coding situations. I used regex, string operations and the relatively new Span API . I deliberately left out vectorization, e.g. with the help of Vector128 , which will be the most performant solution. Vector128 is highly optimized, but not an everyday solution.
Code
So I have created a code that uses an input to remove spaces in various ways.
1// Made by Benjamin Abt - https://github.com/BenjaminAbt
2
3using System;
4using System.Buffers;
5using System.Text;
6using System.Text.RegularExpressions;
7using BenchmarkDotNet.Attributes;
8using BenchmarkDotNet.Columns;
9using BenchmarkDotNet.Jobs;
10using BenchmarkDotNet.Running;
11
12
13BenchmarkRunner.Run<Benchmark>();
14
15[MemoryDiagnoser]
16[SimpleJob(RuntimeMoniker.Net80)]
17[SimpleJob(RuntimeMoniker.Net90, baseline: true)]
18[HideColumns(Column.Job)]
19public class Benchmark
20{
21 public const string Input = @"""
22 Hello\u0001World Hello\u0001World Hello\u0001World Hello\u0001World
23 Hello\u0001World Hello\u0001World Hello\u0001World Hello\u0001World
24 Hello\u0001World Hello\u0001World Hello\u0001World Hello\u0001World
25 Hello\u0001World Hello\u0001World Hello\u0001World Hello\u0001World
26 Hello\u0001World Hello\u0001World Hello\u0001World Hello\u0001World
27 Hello\u0001World Hello\u0001World Hello\u0001World Hello\u0001World
28 Hello\u0001World Hello\u0001World Hello\u0001World Hello\u0001World
29 Hello\u0001World Hello\u0001World Hello\u0001World Hello\u0001World
30 """;
31
32 [Benchmark]
33 public string Regex()
34 {
35 return RegexSample.WhiteSpaceRegex().Replace(Input, "");
36 }
37
38 [Benchmark]
39 public string String()
40 {
41 string data = Input;
42
43 return data.Replace(" ", "");
44 }
45
46 [Benchmark]
47 public string Span()
48 {
49 ReadOnlySpan<char> inputSpan = Input.AsSpan();
50 Span<char> resultSpan = stackalloc char[Input.Length];
51 int resultIndex = 0;
52
53 foreach (char c in inputSpan)
54 {
55 if (c is not ' ')
56 {
57 resultSpan[resultIndex++] = c;
58 }
59 }
60
61 return new string(resultSpan.Slice(0, resultIndex));
62 }
63
64 [Benchmark]
65 public string StringBuilder()
66 {
67 StringBuilder stringBuilder = new(Input);
68 stringBuilder.Replace(" ", "");
69
70 return stringBuilder.ToString();
71 }
72
73 [Benchmark]
74 public string JoinSplit()
75 {
76 return string.Join("", Input.Split(default(string[]), StringSplitOptions.RemoveEmptyEntries));
77 }
78
79 [Benchmark]
80 public string ConcatSplit()
81 {
82 return string.Concat(Input.Split(null));
83 }
84
85 [Benchmark]
86 public string SpanArrayPool()
87 {
88 char[] pooledArray = ArrayPool<char>.Shared.Rent(Input.Length);
89 try
90 {
91 Span<char> destination = pooledArray.AsSpan(0, Input.Length);
92
93 int pos = 0;
94
95 foreach (char c in Input)
96 {
97 if (!char.IsWhiteSpace(c))
98 {
99 destination[pos++] = c;
100 }
101 }
102
103 return Input.Length == pos ? Input : new string(destination[..pos]);
104 }
105 finally
106 {
107 ArrayPool<char>.Shared.Return(pooledArray);
108 }
109 }
110
111 [Benchmark]
112 public string SpanStackPool()
113 {
114 // this only works when Input <256 to avoid heap allocation
115 Span<char> destination = stackalloc char[Input.Length];
116
117 int pos = 0;
118
119 foreach (char c in Input)
120 {
121 if (!char.IsWhiteSpace(c))
122 {
123 destination[pos++] = c;
124 }
125 }
126
127 return Input.Length == pos ? Input : new string(destination[..pos]);
128 }
129}
130
131public static partial class RegexSample
132{
133 [GeneratedRegex(@"\s+")]
134 public static partial Regex WhiteSpaceRegex();
135}
Benchmark
I then used benchmarking to measure this code.
1BenchmarkDotNet v0.14.0, Windows 10 (10.0.19045.5131/22H2/2022Update)
2AMD Ryzen 9 9950X, 1 CPU, 32 logical and 16 physical cores
3.NET SDK 9.0.100
4 [Host] : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
5 .NET 8.0 : .NET 8.0.11 (8.0.1124.51707), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
6 .NET 9.0 : .NET 9.0.0 (9.0.24.52809), X64 RyuJIT AVX-512F+CD+BW+DQ+VL+VBMI
7
8
9| Method | Runtime | Mean | Error | StdDev | Ratio | RatioSD | Gen0 | Gen1 | Allocated | Alloc Ratio |
10|-------------- |--------- |-----------:|---------:|---------:|------:|--------:|-------:|-------:|----------:|------------:|
11| Regex | .NET 8.0 | 656.2 ns | 7.17 ns | 6.36 ns | 1.06 | 0.01 | 0.0629 | - | 1.03 KB | 1.00 |
12| Regex | .NET 9.0 | 617.5 ns | 3.67 ns | 3.44 ns | 1.00 | 0.01 | 0.0629 | - | 1.03 KB | 1.00 |
13| | | | | | | | | | | |
14| String | .NET 8.0 | 1,074.5 ns | 9.94 ns | 9.29 ns | 1.21 | 0.01 | 0.0629 | - | 1.05 KB | 1.00 |
15| String | .NET 9.0 | 887.9 ns | 2.59 ns | 2.29 ns | 1.00 | 0.00 | 0.0639 | - | 1.05 KB | 1.00 |
16| | | | | | | | | | | |
17| Span | .NET 8.0 | 288.8 ns | 5.67 ns | 6.31 ns | 1.53 | 0.04 | 0.0639 | - | 1.05 KB | 1.00 |
18| Span | .NET 9.0 | 188.4 ns | 2.61 ns | 2.45 ns | 1.00 | 0.02 | 0.0639 | - | 1.05 KB | 1.00 |
19| | | | | | | | | | | |
20| StringBuilder | .NET 8.0 | 1,042.8 ns | 8.32 ns | 7.78 ns | 1.20 | 0.02 | 0.1411 | - | 2.33 KB | 1.00 |
21| StringBuilder | .NET 9.0 | 871.6 ns | 13.50 ns | 12.63 ns | 1.00 | 0.02 | 0.1421 | - | 2.33 KB | 1.00 |
22| | | | | | | | | | | |
23| JoinSplit | .NET 8.0 | 688.6 ns | 4.47 ns | 4.18 ns | 1.06 | 0.01 | 0.2422 | 0.0010 | 3.97 KB | 1.00 |
24| JoinSplit | .NET 9.0 | 650.9 ns | 7.26 ns | 6.79 ns | 1.00 | 0.01 | 0.2422 | 0.0010 | 3.97 KB | 1.00 |
25| | | | | | | | | | | |
26| ConcatSplit | .NET 8.0 | 680.3 ns | 10.91 ns | 10.20 ns | 1.07 | 0.02 | 0.2251 | 0.0010 | 3.68 KB | 1.00 |
27| ConcatSplit | .NET 9.0 | 634.2 ns | 11.93 ns | 11.15 ns | 1.00 | 0.02 | 0.2251 | 0.0010 | 3.68 KB | 1.00 |
28| | | | | | | | | | | |
29| SpanArrayPool | .NET 8.0 | 312.7 ns | 3.35 ns | 3.13 ns | 0.98 | 0.01 | 0.0629 | - | 1.03 KB | 1.00 |
30| SpanArrayPool | .NET 9.0 | 318.8 ns | 3.48 ns | 3.26 ns | 1.00 | 0.01 | 0.0629 | - | 1.03 KB | 1.00 |
31| | | | | | | | | | | |
32| SpanStackPool | .NET 8.0 | 370.0 ns | 2.87 ns | 2.69 ns | 1.27 | 0.02 | 0.0629 | - | 1.03 KB | 1.00 |
33| SpanStackPool | .NET 9.0 | 291.1 ns | 5.08 ns | 4.75 ns | 1.00 | 0.02 | 0.0629 | - | 1.03 KB | 1.00 |
You can see some enormous differences; StringBuilder , which is actually so performant in many situations, is much slower and generates many more allocations. Regex , on the other hand, is not as bad as you might think. But as you would expect, the various Span variants are all very far ahead in terms of performance - so it’s good that the new Span API is really easy to understand and use.
However, if you need the very best performance, you won’t be able to avoid using AVX2 , for example meziantou’s Replace characters in a string using Vectorization implementation.
Sustainable Code
You can find this and many more examples on my GitHub under Sustainable Code .
Author
BEN ABT
Ben is a Principal Software Engineer at Medialesson.de, with a strong focus on .NET and Microsoft Azure. In his professional role, he designs and builds highly scalable platforms for hybrid and cloud-based scenarios. He also advises companies and C-levels on migrating to the sovereign cloud.
He runs myCSharp.de, the largest and most active German-speaking C# community forum, actively contributes to both his own and external open-source projects, and regularly shares his knowledge through his blog, at community events, conferences, and as a writer for technical magazines.
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