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Enum `std.range.SearchPolicy`

Policy used with the searching primitives lowerBound, upperBound, and equalRange of SortedRange below.


						
				enum SearchPolicy
				 : int { ... }

Enum members

Name	Description
`binarySearch`	Searches using a classic interval halving policy. The search starts in the middle of the range, and each search step cuts the range in half. This policy finds a value in Ο(`log(n)`) time but is less cache friendly than `gallop` for large ranges. The `binarySearch` policy is used as the last step of `trot`, `gallop`, `trotBackwards`, and `gallopBackwards` strategies.
`gallop`	Performs a galloping search algorithm, i.e. searches with a step that doubles every time, (1, 2, 4, 8, ...) leading to an exponential search schedule (indexes tried are 0, 1, 3, 7, 15, 31, 63,...) Once the search overshoots its target, the remaining interval is searched using binary search. A value is found in Ο(`log(n)`) time.
`gallopBackwards`	Similar to `gallop` but starts backwards. Use it when confident that the value is around the end of the range.
`linear`	Searches in a linear fashion.
`trot`	Searches with a step that is grows linearly (1, 2, 3,...) leading to a quadratic search schedule (indexes tried are 0, 1, 3, 6, 10, 15, 21, 28,...) Once the search overshoots its target, the remaining interval is searched using binary search. The search is completed in Ο(`sqrt(n)`) time. Use it when you are reasonably confident that the value is around the beginning of the range.
`trotBackwards`	Similar to `trot` but starts backwards. Use it when confident that the value is around the end of the range.

Example

import std.algorithm.comparison : equal;

auto a = assumeSorted([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
auto p1 = a.upperBound!(SearchPolicy.binarySearch)(3);
assert(p1.equal([4, 5, 6, 7, 8, 9]));

auto p2 = a.lowerBound!(SearchPolicy.gallop)(4);
assert(p2.equal([0, 1, 2, 3]));

Authors

Andrei Alexandrescu, David Simcha, Jonathan M Davis, and Jack Stouffer. Credit for some of the ideas in building this module goes to Leonardo Maffi.

License

Boost License 1.0.