NEOS Interfaces to MUSCOD-II
The NEOS Server offers MUSCOD-II (
e for Optimal Control) for the solution of mixed integer nonlinear ODE- or DAE-constrained optimal control problems in an extended
The AMPL modeling language itself does not allow the formulation of differential equations. Hence, the
has been designed to implement a small set of extensions for easy and convenient modeling of optimal control problems in AMPL, without the need for explicit encoding of discretization schemes (e.g. collocation).
Both the TACO Toolkit and the NEOS interface to MUSCOD-II are still under development.
MUSCOD-II is not in the public domain, but can be licensed from the
Simulation and Optimization group
Interdisciplinary Center for Scientific Computing (IWR)
, Germany. It is a joint development effort by many current and former members of the Simulation and Optimization group at Heidelberg:
Hans Georg Bock and Johannes P. Schlöder,
Daniel B. Leineweber, Moritz Diehl, and Andreas Schäfer,
Christian Hoffmann, Christian Kirches, Andreas Potschka, Sebastian Sager, and Leonard Wirsching,
with contributions from many others.
The TACO Toolkit and the NEOS driver for MUSCOD-II were written and are maintained by Christian Kirches and Sven Leyffer. Developers of optimal control problem solvers can
the TACO Toolkit source code.
The class of tractable problems is described in the
MUSCOD-II User's Manual
. Mixed-integer optimal control problems (MIOCPs) should be submitted in their
Partial Outer Convexification
reformulation. Then, an approximation theorem holds for the convexified and relaxed problem's solution. A variety of algorithms and strategies may be invoked using the
option to obtain an integer feasible solution.
Compared to the C/Fortran interface to MUSCOD-II, the AMPL interface to MUSCOD-II provided through the NEOS server exposes limited functionality only. Restrictions are due to the need to express the model in AMPL syntax. Moreover, some algorithms and problem classes such as model-predictive control and moving horizon estimation don't fit well into the NEOS concept. Users interested in tackling such online optimization problems with direct multiple shooting algorithms are invited to
Using the NEOS Server for MUSCOD-II
The user must submit a model in
format using the
for AMPL Control Optimization extensions, to solve a mixed integer nonlinear ODE- or DAE-constrained optimal control problem. Examples of models in AMPL/TACO format can be found in the open mixed-integer optimal control problem collection at
The model is specified by a model file, and optionally, a data file and a commands file. If the command file is specified it must contain the AMPL solve command.
Quality software requires constant feedback and testing on a realistic set of problems. We hence may collect models you submit, for benchmarking and improving MUSCOD-II.
Solutions are reported in a separate plain-text file. The
TACO Toolkit paper
describes the simple file format and shows a small AMPL script for reading it. Values for ODE/DAE state trajectories and controls trajectories are reported at shooting node positions. Be aware that ODE/DAE state values are initial values for ODE/DAE initial value problems, and should not simply be interpolated between.
Setting Options for MUSCOD-II
MUSCOD-II has a variety of options that can alter the algorithm's behavior. The
TACO Toolkit paper
has a complete list of those options accessible from AMPL. There are two ways to set options to MUSCOD-II through NEOS. First, the AMPL commands file can contain AMPL commands to set options for MUSCOD-II. Second, the user can specify the name of a local options file
that will be used.
Printing directed to standard out is returned to the user with the output.
Web Submission Form
Enter the location of the ampl model (local file)
Enter the location of the ampl data file (local file)
Enter the location of the ampl commands file (local file)
Enter the location of the MUSCOD-II options file (local file)
Return ampl file
This solver provides an output file containing the solution.
Dry run: generate job XML instead of submitting it to NEOS
Short Priority: submit to higher priority queue with maximum CPU time of 5 minutes
Please do not click the 'Submit to NEOS' button more than once.
By submitting a job, you have accepted the