package unionFind

CHANGES

2025/08/18

• A concurrent union-find algorithm is now available under the name UnionFind.Concurrent.
• OCaml 4.12 is now required. (make test requires OCaml 5.0.)
• Fixed and improved documentation for union and merge.

2022/01/22

• Strengthen the specification of merge. It is now guaranteed that, if the user function f raises an exception, then the union-find data structure is unaffected.

2022/01/09

• In UnionFind and UnionFind.Make, introduce a new operation merge, a variant of union that is parameterized with a join function f. The function f is not allowed to perform reentrant accesses to the union-find data structure.
• In UnionFind only, introduce an optimization that reduces the amount of memory allocation. This leads to a speed improvement of about 10% in the micro-benchmark.

2022/01/07

• Incompatible changes in the signature STORE, which appears in the type of the functor UnionFind.Make.

  • Instead of having every operation return a possibly-updated store, we assume that stores are updated in place. A new copy operation is introduced, so a persistent store is now simulated by a mutable store that can be copied in constant time. The main motivation for this change is that it makes UnionFind.Make much more pleasant to use in practice.
  • The operation union is no longer parameterized with a join function f. This API was flawed and could lead to meaningless behavior if the function f provided by the user performed reentrant calls to the union-find algorithm.
  • The operation union now returns a reference of type 'a rref instead of a unit value. This makes UnionFind.Make analogous to UnionFind, which it was not.
• Expose find among the operations offered by UnionFind.Make.
• Add is_representative to the operations offered by UnionFind and by UnionFind.Make.
• Add a micro-benchmark, which is executed by make test.

2022/01/01

• Improved documentation.

2020/03/20

• Add a fast path (an optimization) in the find and eq functions, both in the basic union-find (UnionFind) and the one that is parameterized over a store (UnionFind.Make).

2019/08/27

• Initial release of the package.