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LP solver support

Some configurations of the search component of Fast Downward, such as optimal cost partitioning for landmark heuristics, require an Linear Programming (LP) solver and will complain if the planner has not been built with support for such a solver.

Fast Downward uses the COIN-OR LP Solver (CLP) with the Open Solver Interface.

Instructions for building Fast Downward with LP support

To enable LP support in Fast Downward, you need OSI and (optionally but recommended) an external solver such as CPLEX installed on your system (see below). Once OSI is installed, change the line 

USE_LP=0

in the Makefile to 

USE_LP=1

and run 

make clean
make

Installing CPLEX

IBM has a free academic license that includes access to CPLEX. Once you are registered, you can download a binary from the member area of the Academic Initiative Website. Execute the binary and follow the guided installation. If you want to install in a global location, you have to execute the installer as root.

After the installation, set the following environment variables (you may need different paths if you did not install in the default location). 

    CPLEX_INCDIR=/opt/ibm/ILOG/CPLEX_Studio1251/cplex/include/ilcplex
    CPLEX_LIBDIR=/opt/ibm/ILOG/CPLEX_Studio1251/cplex/lib/x86_sles10_4.1/static_pic

Installing the Open Solver Interface

OSI provides a common interface to different LP solvers. To build an interface to a solver, the solver has to be installed before compiling OSI. If you install a solver later, repeat the installation steps of OSI to use it in Fast Downward.

For this instruction, we assume that CPLEX and gurobi are installed and the environment variables CPLEX_INCDIR, CPLEX_LIBDIR, GUROBI_INCDIR, and GUROBI_LIBDIR are set up correctly. We only tested CPLEX so far but other sovlers should work analogously. Include options for (only) the solvers you have installed.

In the following description we assume version 0.103.0 of COIN/OSI since this was the last version that was bundled with Fast Downward. However, it should also work with the newest version from http://www.coin-or.org/download/source/Osi/ 

wget http://www.coin-or.org/download/source/Osi/Osi-0.103.0.tgz
tar xvzf Osi-0.103.0.tgz
cd Osi-0.103.0

sudo ./configure CC="gcc"  CFLAGS="-m32 -pthread -Wno-long-long" \
                 CXX="g++" CXXFLAGS="-m32 -pthread -Wno-long-long" \
                 LDFLAGS="-L$CPLEX_LIBDIR -L$GUROBI_LIBDIR" \
                 --without-lapack --enable-static=yes \
                 --prefix="/opt/coin"
                 --with-cplex-incdir=$CPLEX_INCDIR --with-cplex-lib="-lcplex -lm"
                 --with-gurobi-incdir=$GUROBI_INCDIR --with-gurob-lib="-lgurobi"
sudo make
sudo make install
cd ..
rm -rf Osi-0.103.0
rm Osi-0.103.0.tgz

After the installation, set the environment variable COIN_ROOT to the prefix you used in the call to ./configure.

If LP setup fails

The LP solver has a number of dependencies which might not be installed on your system. If for some reason the LP setup step fails, we'd appreciate if you attempt to troubleshoot it yourself. Check the contents of the setup script in the lp directory to see what it does, try to run the various steps manually, have a look at the errors generated, and consult the Osi documentation.

If after troubleshooting you can get the LP package to work, do let us know of your problem and its solution so that we can improve these instructions. If you still cannot get it to work, we may be able to provide some help, but note that the LP solver is an external package not developed by us.