H48: prototype for a new optimal solver and nissy backend
Warning: this library is work in progress, breaking changes can happen without notice.
H48 is an experimental Rubik’s cube solver. The main goal is experimenting with various optimal solving methods and pruning tables, with nxopt and vcube as inspiration and benchmark reference.
In the future this project may evolve as a new “back-end” for the classic nissy.
Building
First run the configuration script to detect the system configuration. This is going to select a C compiler and architecture-specific optimizations.
$ ./configure.sh
These settings can be overridden, for example:
$ THREADS=3 CC=gcc ./configure.sh # Use 3 threads and compile with gcc
All the configuration-time options are described in the configure.sh script.
Once the configuration is done, you can build with make
$ make
Running tests
This project includes a suite of “unit” test. They can be run with:
$ make test
To run only a subset of the tests, set the TEST variable to a regular
expression that matches only the name of the tests you want to run:
$ TEST=coord make test
Each subfolder of the test folder contains a test. A test can consist of multiple test cases (.in files). Running a test means compiling and running the corresponding test against each test case. When a test case is run, the .in file is read a the output of the program is compared to the corresponding .out filei using diff(1). If the two differ, the difference is printed out and no other test is run.
The results of the last test case run is saved in test/last.out (standard output, the results compared with the .out files) and test/last.err (standard error).
Tests are always run in debug mode: this means that optimizations are disabled and some extra logging is enabled.
See the test folder and test/test.sh for details.
Running “tools”
In the tools folder there are some small programs that test various functionality of the H48 library. They work similarly to test, but they are not run in debug mode by default.
To run a tool you must select it with the environment variable TOOL.
For example the command:
TOOL=stats make tool
Will run the statstablesh48 tool.
To pass some arguments to a tool, use the TOOLARGS variable:
TOOL=gendata TOOLARGS="h48 0;2;20" make tool
Like for tests, the value of the TOOL variable can be any regular
expression matching the name of the tool. Unlike tests, one and
only one tool will be selected for each run. The content of the
TOOLARGS variable is used directly as command line arguments for
the chosen tool.
Each tool run is automatically timed, so these tools can be used as benchmark. The output as well as the time of the run are saved to a file in the tools/results folder.
To build and run a tool in debug mode, use make debugtool.
User interfaces
User interfaces for this software are in an experimental stage. Some examples are included in this repository, but they are not polished. If you are a developer and you are interested in contributing, have a look at the examples and let me know!
Command-line interface
The shell folder contains the code for a rudimentary shell that can
be used to run commands manually. The user experience in not amazing,
as the commands require quite verbose options.
To build the shell run:
$ make shell
This will create an executable called run.
Optionally, you can run some tests:
$ make shelltest
Then you can for example get a cube from a sequence of moves:
$ ./run frommoves -moves "R' U' F"
JLQWSVUH=ZLCUABGIVTKH
Or you can get a random cube
$ ./run randomcube
WDSQREVX=VBKYDUCJXWAb
If you don’t like this format, you can convert it:
$ ./run convert -fin B32 -fout H48 -cubestr "WDSQREVX=VBKYDUCJXWAb"
UL1 UB0 BL0 FR1 DF0 UR1 DB0 FL0 DR1 DL1 UF0 BR1 DFR2 DBR0 DFL2 UFR2 UBL2 UFL0 UBR2 DBL2
To solve a cube you can use:
$ ./run solve -solver h48h0k4 -n 1 -M 4 -cube "JLQWSVUH=ZLCUABGIVTKH"
F' U' R
Or alternatively:
$ ./run solve_scramble -solver h48h0k4 -n 1 -M 4 -moves "R' U' F"
F' U' R
For a full list of available command, use ./run help.
QT
A draft for a QT-based GUI is contained in the qt folder. In order
to build it you need QT libraries and headers (for QML / QT Quick
development) and CMake. If your environment is set up, you can
build the QT GUI with
$ make qt
And then run it with
$ ./nissyqt
Using this software as a library
This tool has been developed as a library, so it can be easily included in other programs. For this reason, some bindings for languages other than C are available.
The API is documented in the public header file src/nissy.h.
C
To use this in a C project, simly include src/nissy.h. The tools
in the tools/ folder are a good example for how to use this.
NOTE: this project is developed using the C11 standard. If you are using an older version of C, you can write your own header file.
C++
The cpp folder contains a C++ header nissy.h (C++20 standard) and an
implementation file nissy.cpp. This interface wraps the calls to the
C functions in an object-oriented C++ interface for more convenient use.
The cpp/examples folder contains some examples for how to use this
interface. You can build them with e.g.
g++ -std=c++20 cpp/nissy.cpp cpp/examples/solve_h48h3k2.cpp nissy.o
NOTE: If you prefer to use a C-style API, you’ll have to write
your own header, similar to the extern "C" {} block at the top of
cpp/nissy.cpp. The C header src/nissy.h cannot be compiled as C++,
as it uses features of C that are not compatible with it.
Python
The python folder contains a Python module. The API provided by
this module follows the C API quite closely, except its functions
sometimes return strings instead of writing to char * buffers.
To build the Python module you need the Python development headers
installed. You can check this from the output of ./configure.sh:
$ ./configure.sh
...
Python3 development libraries: version 3.12
Then to build the module:
$ make python
And to import it
$ python # In the main folder
>>> import nissy_python_module as nissy # In the python shell
From here you can call the library functions directly, for example:
>>> nissy.compose("NEORSQLH=ZFCYUAGLHTKB", "NEORSQLH=ZFCYUAGLHTKB")
'ASTUGFBH=DACXEZGBLIKF'
The python/examples folder contains some examples, that you
can run for example with:
$ python python/examples/solve.py
You can access the documentation for the Python module from within
a Python interpreter with help(nissy). Cross-check this documentation
with the comments in nissy.h for more details.
NOTE: Support for the Python module is still rudimentary.
Cube formats
The cube is represented as a string in one of the following formats, all explained below:
- H48
- LST
- B32 (the default)
In all of the formats, the permutation of the center pieces is not stored. This means that the cube is assumed to be in a fixed orientation.
More formats will become available in the future.
Cube format: H48
In the H48 format, each edge is represented by two letters denoting the sides it belongs to and one number denoting its orientation (0 oriented, 1 mis-oriented). Similarly, each corner is represented by three letters and a number (0 oriented, 1 twisted clockwise, 2 twisted counter-clockwise).
The solved cube looks like this:
UF0 UB0 DB0 DF0 UR0 UL0 DL0 DR0 FR0 FL0 BL0 BR0 UFR0 UBL0 DFL0 DBR0 UFL0 UBR0 DFR0 DBL0
The cube after the move F looks like this:
FL1 UB0 DB0 FR1 UR0 UL0 DL0 DR0 UF1 DF1 BL0 BR0 UFL1 UBL0 DFR1 DBR0 DFL2 UBR0 UFR2 DBL0
Whitespace (including newlines) between pieces is ignored when reading the cube. A single whitespace character is added between pieces when writing.
You can find more examples of this format in the utils/cubes folder.
Cube format: LST
In the LST format, a cube is represented by a comma-separated list of integers. Each piece is represented by an (unsigned) 8-bit integer. The 4 least-significant bits determine which piece it is, the other 4 determine the orientation.
Edges are numbered as follows (see also constants.h):
UF=0 UB=1 DB=2 DF=3 UR=4 UL=5 DL=6 DR=7 FR=8 FL=9 BL=10 BR=11
Corners are numbered as follows:
UFR=0 UBL=1 DFL=2 DBR=3 UFL=4 UBR=5 DFR=6 DBL=7
The orientation of the edges is with respect to F/B, the orientation of corners is with respect to U/D.
In this format, the solved cube looks like this:
0, 1, 2, 3, 4, 5, 6, 7, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11
The cube after the move F looks like this:
36, 1, 38, 3, 66, 5, 64, 7, 25, 1, 2, 24, 4, 5, 6, 7, 16, 19, 10, 11
Cube format: B32
This format is a “base 32” encoding of the cube. It is not meant to be human-readable, but it is compact while still being plain text. Each piece, including the orientation value, is encoded as a number from 0 to 31, and this number is then converted to an uppercase letter (0-26) or to a lowercase letter (27-31). Edges and corners are separated by a single = character.
In this format, the solved cube looks like this:
ABCDEFGH=ABCDEFGHIJKL
The cube after the move F looks like this:
MBODSFQH=ZBCYEFGHQTKL
A cube in B32 format is always 21 characters long (22 if the terminating null character is included).