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47 lines
2.4 KiB
Markdown
47 lines
2.4 KiB
Markdown
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uint128
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-------
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[](https://godoc.org/github.com/lukechampine/uint128)
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[](https://goreportcard.com/report/github.com/lukechampine/uint128)
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```
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go get lukechampine.com/uint128
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```
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`uint128` provides a high-performance `Uint128` type that supports standard arithmetic
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operations. Unlike `math/big`, operations on `Uint128` values always produce new values
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instead of modifying a pointer receiver. A `Uint128` value is therefore immutable, just
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like `uint64` and friends.
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The name `uint128.Uint128` stutters, so I recommend either using a "dot import"
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or aliasing `uint128.Uint128` to give it a project-specific name. Embedding the type
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is not recommended, because methods will still return `uint128.Uint128`; this means that,
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if you want to extend the type with new methods, your best bet is probably to copy the
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source code wholesale and rename the identifier. ¯\\\_(ツ)\_/¯
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# Benchmarks
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Addition, multiplication, and subtraction are on par with their native 64-bit
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equivalents. Division is slower: ~20x slower when dividing a `Uint128` by a
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`uint64`, and ~100x slower when dividing by a `Uint128`. However, division is
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still faster than with `big.Int` (for the same operands), especially when
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dividing by a `uint64`.
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```
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BenchmarkArithmetic/Add-4 2000000000 0.45 ns/op 0 B/op 0 allocs/op
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BenchmarkArithmetic/Sub-4 2000000000 0.67 ns/op 0 B/op 0 allocs/op
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BenchmarkArithmetic/Mul-4 2000000000 0.42 ns/op 0 B/op 0 allocs/op
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BenchmarkArithmetic/Lsh-4 2000000000 1.06 ns/op 0 B/op 0 allocs/op
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BenchmarkArithmetic/Rsh-4 2000000000 1.06 ns/op 0 B/op 0 allocs/op
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BenchmarkDivision/native_64/64-4 2000000000 0.39 ns/op 0 B/op 0 allocs/op
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BenchmarkDivision/Div_128/64-4 2000000000 6.28 ns/op 0 B/op 0 allocs/op
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BenchmarkDivision/Div_128/128-4 30000000 45.2 ns/op 0 B/op 0 allocs/op
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BenchmarkDivision/big.Int_128/64-4 20000000 98.2 ns/op 8 B/op 1 allocs/op
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BenchmarkDivision/big.Int_128/128-4 30000000 53.4 ns/op 48 B/op 1 allocs/op
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BenchmarkString/Uint128-4 10000000 173 ns/op 48 B/op 1 allocs/op
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BenchmarkString/big.Int-4 5000000 350 ns/op 144 B/op 3 allocs/op
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```
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