The psqueues package provides Priority Search Queues in three different flavors.
OrdPSQ k p v, which uses the
Ord kinstance to provide fast insertion, deletion and lookup. This implementation is based on Ralf Hinze's A Simple Implementation Technique for Priority Search Queues. Hence, it is similar to the PSQueue library, although it is considerably faster and provides a slightly different API.
IntPSQ p vis a far more efficient implementation. It fixes the key type to
Intand uses a radix tree (like
IntMap) with an additional min-heap property.
HashPSQ k p vis a fairly straightforward extension of
IntPSQ: it simply uses the keys' hashes as indices in the
IntPSQ. If there are any hash collisions, it uses an
OrdPSQto resolve those. The performance of this implementation is comparable to that of
IntPSQ, but it is more widely applicable since the keys are not restricted to
Int, but rather to any
Each of the three implementations provides the same API, so they can be used interchangeably. The benchmarks show how they perform relative to one another, and also compared to the other Priority Search Queue implementations on Hackage: PSQueue and fingertree-psqueue.
Typical applications of Priority Search Queues include:
Caches, and more specifically LRU Caches;
Pathfinding algorithms, such as Dijkstra's and A*.