OPTIC: Optimising Preferences and Time-Dependent Costs



OPTIC is a temporal planner for use in problems where plan cost is determined by preferences or time-dependent goal-collection costs. Such problems arise in a range of interesting situations, from scheduling the delivery of perishable goods, to coordinating order-fulfillment activities in warehouses.

OPTIC was described in the award-winning ICAPS 2012 paper 'Temporal Planning with Preferences and Time-Dependent Continuous Costs" , by J. Benton, Amanda Coles, and Andrew Coles. In the interests of developing a single, capable planner, OPTIC also includes the TIL-abstraction extension of POPF described in the paper "Automated Planning for Liner Shipping Fleet Repositioning", K. Tierney, A. J. Coles, A. I. Coles, C. Kroer, A. Britt, and R. M. Jensen, ICAPS 2012.

Build Prerequisites

OPTIC requires either CLP or CPLEX:

  • If you wish to use OPTIC in problems with Preferences or in which TIL abstraction is used, you will need CPLEX. For academic use, CPLEX can be obtained for free via the IBM Academic Initiative.
  • In other cases, CLP should suffice, and is generally faster.

If you are opting to compile OPTIC from sources, you also need:

  • cmake
  • perl, bison and flex (used to build the parser)


Packages of these are available for most linux distributions. For Ubuntu, the following should install CLP and the other build pre-requisites:

sudo apt-get install cmake coinor-libcbc-dev coinor-libclp-dev \
                     coinor-libcoinutils-dev coinor-libosi-dev coinor-libcgl-dev doxygen libbz2-dev bison flex



Compiling from Sources


Compilation is in two stages:

1) Configure

Run one of:

  • run-cmake-debug, if you want to link against CLP, with debugging enabled
  • run-cmake-for-cplex-debug-x86, if you want to link against CLP and/or CPLEX, with debugging enabled. It assumes you are using the 32-bit version of CPLEX, on Linux - if this is not the case, edit the script.
  • run-cmake-release, if you want to link against CLP, with debugging disabled, and producing a non-static binary.
  • run-cmake-static, if you want to link against CLP, with debugging disabled, and producing a statically linked binary
  • run-cmake-for-cplex-static-x86, if you want to link against CLP and/or CPLEX, and producing a statically linked binary. It assumes you are using the 32-bit version of CPLEX, on Linux - if this is not the case, edit the script.

Note that if you want to make static binaries with CLP, you must have static versions of the CLP libraries installed. This may mean downloading and compiling CBC from source, making sure it makes static (not shared) libraries. The advantage is that the binary produced does not require CLP to be installed at run-time, which can be useful when running it on different machines.

Users of 64-bit Machines: it is almost certainly not worth compiling OPTIC in 64-bit mode. To force 32-bit compilation, before running one of the scripts above, type:

export CFLAGS=-m32
export CXXFLAGS=-m32
export LDFLAGS=-m32


In 32-bit mode, OPTIC it is limited by the number of states it can store in 4GB of memory. To be able to store more states than this, with a 64-bit binary, considerably more memory is required, as e.g. ints and pointers are twice the size. (If you do have considerably more memory, then of course, feel free to try.)

2) Build

If you ran one of the run-*-debug scripts, now run:

./build-debugging

If you ran run-cmake-release, now run:

./build-release

If you ran one of the run-*-static scripts, now run:

./build-static


In all three cases, the binaries produced will be called optic-clp and/or optic-cplex, and they will be located in either debug/optic, release/optic or static/optic, respectively.


Running


Once compiled, run, e.g.:

optic-cplex domain.pddl problem.pddl

This runs OPTIC on the given domain and problem file, carrying on search after the first solution in an attempt to optimise quality. If you want to ignore solution costs and stop after the first solution, run:

optic-cplex -N domain.pddl problem.pddl

Or, if you have an upper-bound on plan cost (e.g. 100), run:

optic-cplex -n100 domain.pddl problem.pddl

To enable TIL abstraction, add the command-line option '-0', e.g.:

optic-cplex -0 domain.pddl problem.pddl

On domains without preferences, and where TIL-abstraction is not enabled. it is usually faster to use optic-clp instead of optic-cplex. It is run in the same way, e.g.:

optic-clp domain.pddl problem.pddl

If you wish to insist that each solution has to be at least 10 better than the last found, run:

optic-clp '->10' domain.pddl problem.pddl

Note that the planner does not, itself, limit its time and/or memory usage. Apply these by using the relevant shell commands beforehand, e.g.:

bash
ulimit -t 1800
ulimit -v 4000000
./optic-clp domain.pddl problem.pddl


...will limit the planner to 30 minutes of CPU and 4GiB of memory.

Feedback


If you do something exciting with OPTIC, do let us know. If you tried to do something with it, but it failed, you may have found a bug. In common with POPF, the three most likely sources of bugs are:

The three most common causes of bugs (over 90% of bug reports) are:

  • Using ADL. ADL is supported in the conditions of preferences, in the time-dependent costs of goal-collection actions, and one or two other niche cases. We've attempted to make the planner degrade gracefully, but there are still cases where it will report problems using ADL as being unsolvable. Check there are no negative preconditions in your domain.
  • Domain modelling bugs. OPTIC and POPF support the full start--end semantics of PDDL 2.1, and self-overlapping actions, so errors in the temporal placement of preconditions and effects (at start, at end etc.) are more likely to cause issues with POPF than with other planners. For instance, if a 'move' action is written (erroneously) as deleting the old location at the end (rather than at the start), then POPF will consider concurrent move actions for the same vehicle; whereas planners which do not make as clear a distinction between the start and end-points of durative actions would not consider this. Thus, in domains with errors such as this, POPF might have to consider a far larger search space than other temporal planners.
  • If the plans don't validate, ensure you are passing the '-t 0.001' flag to VAL: the planner uses an epsilon value of 0.001, smaller than the default 0.01 value used in VAL.


If none of those apply, email as small a possible domain and problem file that cause the error you're observing to Andrew Coles: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

Licence


OPTIC is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 2 of the License, or (at your option) any later version.

OPTIC is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.