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This rewrite improves the core data structure implementation in two ways. Firstly, when merging two equivalence classes, we check their relative sizes, and choose the larger class's canonical element to be the overall root of the new class tree. This minimises the number of overlong paths to the root after the merge. Secondly, we defer path compression until _after_ the two classes are merged, rather than do it beforehand (via using edsf_canonify as a subroutine) and then have to do it wastefully again afterwards. The size-based root selection was what we _used_ to do, and delivers the better asymptotic performance. I reverted it so that Keen could track the min of each equivalence class. But since then I've realised you can have the asymptotic goodness _and_ min-tracking if you store the minima separately from the main data structure. So now Keen does that, and other clients don't have to pay the cost. Similarly, the flip tracking is now a cost that only users of flip dsfs have to pay, because a normal one doesn't store that information at all.
This is the README accompanying the source code to Simon Tatham's puzzle collection. The collection's web site is at <https://www.chiark.greenend.org.uk/~sgtatham/puzzles/>. The puzzle collection is built using CMake <https://cmake.org/>. To compile in the simplest way (on any of Linux, Windows or Mac), run these commands in the source directory: cmake . cmake --build . The manual is provided in Windows Help format for the Windows build; in text format for anyone who needs it; and in HTML for the Mac OS X application and for the web site. It is generated from a Halibut source file (puzzles.but), which is the preferred form for modification. To generate the manual in other formats, rebuild it, or learn about Halibut, visit the Halibut website at <https://www.chiark.greenend.org.uk/~sgtatham/halibut/>.