Optimization problems occasionally yield unbounded solutions. To find the cause one can modify the model and solve it to gain information. This is done through the imposition of “artificially” large bounds. Linear programming solvers discover unboundedness when they find a variable which is attractive to make larger, but find that the variable may be increased without limit. In GAMS some solvers return such information but typically only one unbounded variable will be reported, if any and there may be numerous other variables which have not been examined and could be unbounded. Unfortunately, the LST file does not generally give enough information to diagnose and fix the cause of the unboundedness and pre-solves rarely find such problems. Commonly, the solution report contains an instance where a particular item is tagged as unbounded (with the marker UNBND), but there will also be other variables marked as non-optimal (NOPT) which may or may not be unbounded. Finally, note that use of GAMSCHK ANALYSIS and correction of all identified problems and models still can be bounded. Thus, most modelers will occasionally contend with models that are unbounded and will need to discover what is causing that condition.
MIRO Features Conference Report
TIMES is a sophisticated energy model generator implemented in GAMS. It has been published under an open source license in 2019. Recently, GAMS joined forces with experienced TIMES users to develop an open-source TIMES/MIRO App that serves as a frontend to the TIMES model. This was made possible by new features in GAMS MIRO 1.1
Energy system optimization modeling has become a key ingredient in transitioning to decarbonized energy supply systems based mostly on renewables. Yet, these systems reveal a growing complexity, e.g., due to the decentralization of infrastructures or an increasing variety of potential technologies capable of balancing energy demand and supply. This renders a reliable application of traditional optimization modeling techniques impossible.
Given the crucial role power distribution plays for the economy, and the challenges posed by renewable energy and increasing demand for electricity, ARPA-E is running the Grid Optimization Competition, which challenges participating teams to develop and test power system optimization and control algorithms on a range of different synthetic and real network models. This is another great example of how modeling and optimization impacts our lives and society! Watch the U.S. DOE competition announcement below:
General GAMS Update News Sales
Some of you might have noticed that coincident with releasing GAMS 30.1, we have introduced some changes to our licensing model . Below we summarize what has changed.
We have changed the way we allow users to test GAMS (“demo mode”). We now require registration on our website and generating a demo license before using the software. Some might find this process annoying, but before introducing this new scheme, we simply did have no idea how many people were using GAMS in demo mode. For a company trying to understand and serve its customer base, this was utterly unsatisfactory. With the new scheme, we collect and process some personal data, which we use to generate a named license file - after all, demo licenses are not meant to be shared between users. Four weeks later, all personal data is automatically deleted (names, email-address, IP-address, even the license file itself). We keep just enough data to compile statistics about how many demo licenses have been generated over time, and which countries and organisations these licenses are popular in.
Atharv Bhosekar
Adam Christensen
Aileen Homey
Alexander Meeraus
André Schnabel
Bruce McCarl
Christophe Gouel
Clemens Westphal
Evangelos Panos
Fred Fiand
Freddy Proske
George Franco
Hans Lofgren
Justine Broihan
Julien Harou
Janina Hasselbring
Leonard Kunz
Logan Randolph
Lutz Westermann
Mohammed Basheer
Marius Bützler
Michael Bussieck
Mateo Gallia
Michael Horstmann
Renke Kuhlmann
Robin Schuchmann
Steve Dirkse
Stefan Mann