Heuristic for MIP 2022 competition.

Requirements
------------

- CMake >= 3.12
- CPLEX >= 12.10
- Recent C++ compiler supporting some C++20 (gcc >= 10.0 and clang >= 11.0)

Build
-----

Users have to specify a path to the CPLEX installation by passing the
setting the cmake variable CPLEX_ROOT_DIR. Except for this, compilations
follows the usual cmake steps:

mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DCPLEX_ROOT_DIR=${PATH_TO_CPLEX_INSTALLATION} ..

Usage
-----

There are two binaries: fpr and tryfpr.
The first implement the overall portfolio approach, while the second
runs only a single variant at the time.
Usage is quite similar. For example:

./tryfpr run=dfs strategy=lp timeLimit=1000 instance.mps

Runs and strategies can be specified only for the tryfpr binary,
as fpr will just run the hard-coded portfolio (and ignore run
and strategy settings from the command line). For tryfpr,
you can set either "run" or "strategy" to an empty value to get
the list of available values. Resource limits (like time limit,
threads, etc...) can be set for both binaries.

It is also possible to save the best solution found (if any) to a file
by just passing the option 'saveSol=1'. This will save the solution to
a file named instance.sol.

The solution itself can be checked with the solchecker binary:

./solchecker instance.mps instance.sol