BusterWood.Collections
UniqueList
UniqueList is a generic collection that is both a set and a list:
- implements
ISet<T>and has hash table like performance forContainsandIndexOfoperations - implements
IList<T>and gives constant time access to items via index - stores values in an array, so enumeration yields items in list order, i.e. in the order they were added
- does not allow null to be added - calling
Add()with a null value always returns FALSE and does not add to the underlying list of values
The design of UniqueList was inspired by Python 3.6's new dict which uses hashcode to access an array of indexes which gives an index into the array of values.
Add Performance
Add performance is similar to a adding to a HashSet<T> and not that much slower than List<T>, for example adding a number strings:
BenchmarkDotNet=v0.10.8, OS=Windows 10 Redstone 1 (10.0.14393)
Processor=AMD A4-6210 APU with AMD Radeon R3 Graphics, ProcessorCount=4
Frequency=1754521 Hz, Resolution=569.9561 ns, Timer=TSC
[Host] : Clr 4.0.30319.42000, 64bit RyuJIT-v4.7.2101.1
DefaultJob : Clr 4.0.30319.42000, 64bit RyuJIT-v4.7.2101.1
Method | Size | Mean | Error | StdDev |
----------- |----- |------------:|------------:|------------:|
UniqueList | 50 | 29.79 us | 0.5882 us | 0.5777 us |
ArrayList | 50 | 22.06 us | 0.4055 us | 0.3793 us |
HashSet | 50 | 28.81 us | 0.5722 us | 0.5353 us |
UniqueList | 500 | 327.05 us | 6.4500 us | 11.1260 us |
ArrayList | 500 | 234.22 us | 4.6396 us | 5.6979 us |
HashSet | 500 | 304.02 us | 5.9085 us | 9.3715 us |
UniqueList | 5000 | 3,350.63 us | 70.5560 us | 58.9174 us |
ArrayList | 5000 | 2,478.81 us | 56.2821 us | 64.8145 us |
HashSet | 5000 | 5,107.88 us | 100.1957 us | 143.6977 us |
Contains / IndexOf performance
Contains performance is similar to a HashSet<T> and much faster than List<T>, for example lookup up all the strings in a list or set of different sizes:
BenchmarkDotNet=v0.10.8, OS=Windows 10 Redstone 1 (10.0.14393)
Processor=AMD A4-6210 APU with AMD Radeon R3 Graphics, ProcessorCount=4
Frequency=1754521 Hz, Resolution=569.9561 ns, Timer=TSC
[Host] : Clr 4.0.30319.42000, 64bit RyuJIT-v4.7.2101.1
DefaultJob : Clr 4.0.30319.42000, 64bit RyuJIT-v4.7.2101.1
Method | Size | Mean | Error | StdDev |
----------- |----- |--------------:|--------------:|--------------:|
UniqueList | 50 | 23.60 us | 0.4546 us | 0.4668 us |
ArrayList | 50 | 56.86 us | 1.1189 us | 1.6401 us |
HashSet | 50 | 24.01 us | 0.4411 us | 0.4126 us |
UniqueList | 500 | 243.04 us | 4.6906 us | 5.0189 us |
ArrayList | 500 | 3,697.55 us | 73.0742 us | 68.3536 us |
HashSet | 500 | 246.22 us | 4.4495 us | 3.7155 us |
UniqueList | 5000 | 2,716.73 us | 52.8352 us | 56.5331 us |
ArrayList | 5000 | 350,595.46 us | 6,076.2343 us | 5,386.4229 us |
HashSet | 5000 | 2,750.42 us | 16.3910 us | 11.8517 us |
Memory usage
UniqueList<T> uses more memory than List<T> but less than HashSet<T>, for example on a x64 system, where T is string:
Data structure | Size | Memory Held |
-------------- |----- |------------ |
UniqueList | 50 | 1.0 K |
ArrayList | 50 | 0.6 K |
HashSet | 50 | 1.7 K |
UniqueList | 500 | 8.6 K |
ArrayList | 500 | 4.5 K |
HashSet | 500 | 18.3 K |
UniqueList | 5000 | 139 K |
ArrayList | 5000 | 73 K |
HashSet | 5000 | 168 K |