This directory contains a in-developent C++ port of Minigo.

The C++ Minigo port uses the Bazel build system. It depends on the Tensorflow C++ libraries, but we have not yet set up Bazel WORKSPACE and BUILD rules to automatically download and configure Tensorflow so (for now at least) you must perform a manual step to build the library:

./cc/configure_tensorflow.sh

If you want to compile for CPU and not GPU, then change TF_NEED_CUDA to 0 in configure_tensorflow.sh

This will automatically perform the first steps of Installing Tensorflow from Sources but instead of installing the Tensorflow package, it extracts the generated C++ headers into the cc/tensorflow subdirectory of the repo. The script then builds the required Tensorflow shared libraries and copies them to the same directory. The tensorflow cc_library build target in cc/BUILD pulls these header & library files together into a format the Bazel understands how to link against.

The C++ Minigo implementation requires that the board size be defined at compile time, using the MINIGO_BOARD_SIZE preprocessor define. This allows us to significantly reduce the number of heap allocations performed. However, it does mean that you must specify the board size when compiling by invoking Bazel with either --define=board_size=9 or --define=board_size=19. This defines MINIGO_BOARD_SIZE when compiling the Minigo sources, but none of their dependencies, which avoids unnecessarily recompiling Minigo's dependencies when switching board size.

Pass --define=board_size=9 when invoking Bazel to build Minigo for a 9x9 board.

Pass --define=board_size=19 when invoking Bazel to build Minigo for a 19x19 board.

Minigo's C++ unit tests operate on both 9x9 and 19x19, and some tests are only enabled for a particular board size. Consequently, you must run the tests multiple times:

bazel test --define=board_size=9 cc/...  &&  bazel test --define=board_size=19 cc/...

The C++ Minigo binary requires the model to be provided in GraphDef binary proto format.

To run Minigo with a 9x9 model:

bazel build --config=minigo9 -c opt cc:main
bazel-bin/cc/main --model=$MODEL_PATH

To run Minigo with a 19x19 model:

bazel build --config=minigo9 -c opt cc:main
bazel-bin/cc/main --model=$MODEL_PATH

The Minigo binary has a lot of command line arguments that configure its behavior, run it with --helpshort to see the full list.

bazel-bin/cc/main --helpshort

The general structure of the C++ code tries to follow the Python code where appropriate, however a lot of the implementation details are different for performance reasons. In particular, the logic that handles the board state strives for a small memory footprint and eschews data structures more sophisticated than a simple array in an effort to minimize memory allocations and maximize cache locality of data. In doing so, the implementation is kept fairly simple (there is no need for a LibertyTracker) and at the time of writing performance of the Position code was more than 450x that of its Python counterpart.

The C++ code follows Google's C++ style guide and we use cpplint to delint.