39 lines
2 KiB
Text
39 lines
2 KiB
Text
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= Bits
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Bits provides methods on a bit array type.
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The Bits type holds a fixed size array of bits, numbered consecutively
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from zero. Some set-like operations are possible, but the API is more
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array-like or register-like.
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image:https://godoc.org/github.com/soniakeys/bits?status.svg[link=https://godoc.org/github.com/soniakeys/bits] image:https://travis-ci.org/soniakeys/bits.svg[link=https://travis-ci.org/soniakeys/bits]
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== Motivation and history
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This package evolved from needs of my library of
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https://github.com/soniakeys/graph[graph algorithms]. For graph algorithms
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a common need is to store a single bit of information per node in a way that
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is both fast and memory efficient. I began by using `big.Int` from the standard
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library, then wrapped big.Int in a type. From time to time I considered
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other publicly available bit array or bit set packages, such as Will
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Fitzgerald's popular https://github.com/willf/bitset[bitset], but there were
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always little reasons I preferred my own type and methods. My type that
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wrapped `big.Int` met my needs until some simple benchmarks indicated it
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might be causing performance problems. Some further experiments supported
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this hypothesis so I ran further tests with a prototype bit array written
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from scratch. Then satisfied that my custom bit array was solving the graph
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performance problems, I decided to move it to a separate package with the
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idea it might have more general utility. For the initial version of this
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package I did the following:
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- implemented a few tests to demonstrate fundamental correctness
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- brought over most methods of my type that wrapped big.Int
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- changed the index type from the graph-specific node index to a general `int`
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- replaced some custom bit-twiddling with use of the new `math/bits` package
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in the standard library
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- renamed a few methods for clarity
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- added a few methods for symmetry
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- added a few new methods I had seen a need for in my graph library
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- added doc, examples, tests, and more tests for 100% coverage
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- added this readme
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