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This is a dedicated algorithm for finding a maximal matching in a bipartite graph. Previously I've been solving that problem in this code base using maxflow.c, modelling the graph matching problem as a restricted case of the optimal network flow problem and then using a full-strength algorithm for the latter. That's overkill, and also algorithmically wasteful - the H-K algorithm is asymptotically better, because it can find multiple augmenting paths in each pass (hence getting the maximum benefit out of each expensive breadth-first search), as a consequence of not having to worry about lower- or higher-value augmenting paths in this restricted problem. So I expect this algorithm to be faster, at least in principle or in large cases, when it takes over the jobs currently being done by maxflow. But that's not the only benefit. Another is that the data representation is better suited to the problems actually being solved, which should simplify all the call sites; a third is that I've incorporated randomisation of the generated matching into the H-K module itself, which will further save effort at each call site because they will no longer have to worry about permuting the algorithm's input - they just have to pass it a random_state and it will take care of that internally. This commit only introduces the new matching.c and builds a test utility for it. I haven't yet migrated any clients of maxflow.
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/>. If you've obtained the source code by downloading a .tar.gz archive from the Puzzles web site, you should find several Makefiles in the source code. However, if you've checked the source code out from the Puzzles git repository, you won't find the Makefiles: they're automatically generated by `mkfiles.pl', so run that to create them. The Makefiles include: - `Makefile.am', together with the static `configure.ac', is intended as input to automake. Run `mkauto.sh' to turn these into a configure script and Makefile.in, after which you can then run `./configure' to create an actual Unix Makefile. - `Makefile.vc' should work under MS Visual C++ on Windows. Run 'nmake /f Makefile.vc' in a Visual Studio command prompt. - `Makefile.cyg' should work under Cygwin / MinGW. With appropriate tweaks and setting of TOOLPATH, it should work for both compiling on Windows and cross-compiling on Unix. - `Makefile.osx' should work under Mac OS X, provided the Xcode tools are installed. It builds a single monolithic OS X application capable of running any of the puzzles, or even more than one of them at a time. - `Makefile.wce' should work under MS eMbedded Visual C++ on Windows and the Pocket PC SDK; it builds Pocket PC binaries. Many of these Makefiles build a program called `nullgame' in addition to the actual game binaries. This program doesn't do anything; it's just a template for people to start from when adding a new game to the collection, and it's compiled every time to ensure that it _does_ compile and link successfully (because otherwise it wouldn't be much use as a template). Once it's built, you can run it if you really want to (but it's very boring), and then you should ignore it. DO NOT EDIT THE MAKEFILES DIRECTLY, if you plan to send any changes back to the maintainer. The makefiles are generated automatically by the Perl script `mkfiles.pl' from the file `Recipe' and the various .R files. If you need to change the makefiles as part of a patch, you should change Recipe, *.R, and/or mkfiles.pl. 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/>.