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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 a linear programming (LP) solver and will complain if the planner has not been built with support for such a solver. Setting up LP support requires three steps, explained below:

  1. Installing one or more LP solvers.
  2. Installing the Open Solver Interface.
  3. Building Fast Downward with LP support.

Step 1. Installing one or more LP solvers

Fast Downward uses a generic interface (see next step) for accessing LP solvers and hence can be used together with different LP solvers. Currently, three LP solvers are supported: CPLEX, Gurobi, and COIN-LP. You can install one, two or all three solvers without causing conflicts. The solver used by the planner is selected by command-line arguments, not at compile time. We recommend using CPLEX, which in our experiments has led to better performance than COIN-LP. We have no experience with Gurobi, but others recommend it over CPLEX. (If you have data comparing these two within Fast Downward, we would be very interested in hearing about it.)

Installing one or more LP solvers: CPLEX

IBM offers 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 (adapt the paths if you did not install in the default location):

export DOWNWARD_CPLEX_INCDIR=/opt/ibm/ILOG/CPLEX_Studio1251/cplex/include/ilcplex
export DOWNWARD_CPLEX_LIBDIR=/opt/ibm/ILOG/CPLEX_Studio1251/cplex/lib/x86_sles10_4.1/static_pic

If you don't want to permanently modify your environment, you can also set these variables directly in src/search/Makefile. The variables need to be set for when installing the Open Solver Interface (Step 2.) and when building Fast Downward's search component (Step 3.).

Installing one or more LP solvers: Gurobi

We have no experience with installing Gurobi.

After the installation, set the following environment variables (adapt the paths if you did not install in the default location):

export DOWNWARD_GUROBI_INCDIR=/path/to/gurobi/include_dir
export DOWNWARD_GUROBI_LIBDIR=/path/to/gurobi/library_dir

If you don't want to permanently modify your environment, you can also set these variables directly in src/search/Makefile. The variables need to be set for when installing the Open Solver Interface (Step 2.) and when building Fast Downward's search component (Step 3.).

Installing one or more LP solvers: COIN-LP

COIN-LP is installed automatically be the following step, so it will be available without additional work. However, we recommend against using it in serious experiments unless you have established that it offers comparable performance to CPLEX in your setting.

Step 2. Installing the Open Solver Interface

The Open Solver Interface (OSI) provides a common interface to different LP solvers. OSI must be compiled after installing the LP solver(s) in Step 1. If you install a solver later, repeat the installation steps of OSI. We assume in the following that CPLEX and Gurobi are installed and the environment variables DOWNWARD_CPLEX_INCDIR, DOWNWARD_CPLEX_LIBDIR, DOWNWARD_GUROBI_INCDIR and DOWNWARD_GUROBI_LIBDIR are set up correctly.

These instructions apply to COIN/OSI 0.103.0, which was the last version that was bundled with Fast Downward. Newer versions from http://www.coin-or.org/download/source/Osi/ should work, too. If you experience problems, please let us know.

Installing the Open Solver Interface on Linux

Run the following commands. If you have installed only one of the two solvers, omit the options for the other one:

   1 wget http://www.coin-or.org/download/source/Osi/Osi-0.103.0.tgz
   2 tar xvzf Osi-0.103.0.tgz
   3 cd Osi-0.103.0
   4 
   5 sudo ./configure CC="gcc"  CFLAGS="-m32 -pthread -Wno-long-long" \
   6                  CXX="g++" CXXFLAGS="-m32 -pthread -Wno-long-long" \
   7                  LDFLAGS="-L$DOWNWARD_CPLEX_LIBDIR -L$DOWNWARD_GUROBI_LIBDIR" \
   8                  --without-lapack --enable-static=yes \
   9                  --prefix="/opt/coin" \
  10                  --with-cplex-incdir=$DOWNWARD_CPLEX_INCDIR --with-cplex-lib="-lcplex -lm" \
  11                  --with-gurobi-incdir=$DOWNWARD_GUROBI_INCDIR --with-gurob-lib="-lgurobi"
  12 sudo make
  13 sudo make install
  14 cd ..
  15 rm -rf Osi-0.103.0
  16 rm Osi-0.103.0.tgz

After installation, set the environment variable DOWNWARD_COIN_ROOT to the prefix you used in the call to ./configure. For example:

export DOWNWARD_COIN_ROOT=/opt/coin

If you don't want to permanently modify your environment, you can also set this variables directly in src/search/Makefile. The variable need to be set when building Fast Downward's search component (Step 3.).

Installing the Open Solver Interface on Mac OS X

Follow the Linux instructions above with the following changes:

Installation has been reported to fail on Mac OS X due to a bug in the CoinUtils configure script. (See issue295.) If you run into this problem, try downloading the patched file attached to this page, make it executable, and replace the file Osi-0.103.0/CoinUtils/configure with it:

    cp Dowloads/coinutils-configure.patched Osi-0.103.0/CoinUtils/configure
    chmod +x Osi-0.103.0/CoinUtils/configure

Step 3. Building Fast Downward with LP support

Once OSI is installed, you can build Fast Downward's search component with LP support by calling make with the option DOWNWARD_USE_LP=1. Remove your previous build first:

make distclean
make DOWNWARD_USE_LP=1

It is also possible to set DOWNWARD_USE_LP directly in src/search/Makefile ore in your environment.

Troubleshooting

The LP-related libraries have a number of dependencies which might not be installed on your system. If for some reason one of the above steps fails, we would appreciate if you could attempt to troubleshoot it yourself.

If the configure step fails for COIN/OSI, have a look at their troubleshooting page. If you get warnings about unresolved references with CPLEX, visit their help pages.

If after troubleshooting you can get the LP package to work, please 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 solvers and OSI library are external packages not developed by us.