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50 lines
1.5 KiB
50 lines
1.5 KiB
# smallmap
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A small table map using single byte key indecies. Designed for maps with tiny keys.
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Pages are stored as 256 entry key-value arrays which are indexed by the byte key index. The key is compared for collision check and on collision the next page is checked or inserted if needed.
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`smallmap` does not ever need to allocate more than 1 page for types which all invariants can be represented as unique bytes.
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## Use cases
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Designed for instances where you want a small map with relatively trivial keys (e.g. primitive type).
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Performance can greately outpace hash-based by an order of magnitude or more in these cases.
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### Maybe use if
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* You have small keys
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* Your map is not at risk of Denial of Service attacks.
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* Your keys will have a lot of collisions
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### Don't use if
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* You have complex keys
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* Denial of service is a concern
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* Your map will contain a large volume of entries
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* Your keys may have a large number of collisions when represented as `u8`.
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# Benchmarks
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Some crude and basic benchmarks
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## char
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| Which | ns/iter |
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|-----------------|---------|
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| `HashMap` | 16 |
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| `smallmap::Map` | 7 |
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## Iterating a string's chars and counting each
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| Which | ns/iter |
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|-----------------|---------|
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| `HashMap` | 8,418 |
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| `BTreeMap` | 9,742 |
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| `smallmap::Map` | 4,416 |
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## u8
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| Which | ns/iter |
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|-----------------|---------|
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| `HashMap` | 15 |
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| `smallmap::Map` | 2 |
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# License
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MIT licensed
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