I found an article on the internet telling that SAP Advanced Planer and Optimizer (APO) uses the ILOG CPLEX optimizer under the hood.
Can you tell me whether it is possible to access the optimizer programmatically in order to solve custom optimization problems?
Related
I realize that this might not be the best platform to ask this, but I think this would be best unbiased one to put my question in.
How would you compare OpenMDAO v/s modeFrontier with regards to there optimization capabilities and application scaling and overall software development? Which one would you pick and why?
If you know of any resources or link do provide.
The most fundamental technical difference is OpenMDAO can pass data + derivative information between components. This means that if you want to use gradient based optimization and have access to at least some tools that provide derivative information, OpenMDAO will have far more effective overall capabilities. This is especially important when doing optimization with high-cost analysis tools (e.g. partial differential equation solvers --- CFD, FEA). In those situations making use of derivatives offers between a 100x and 10000x speedup.
One other difference is that OpenMDAO is designed to run natively on a distributed memory compute cluster. Industrial frameworks can submit jobs to remote clusters and query for the results, but OpenMDAO itself can run on the cluster and has a direct and internal MPI based distributed memory capability. This is critical to it being able to efficiently handle derivatives of those expensive PDE solvers. To the best of my knowledge, OpenMDAO is unique in this regard. This is a low level technical detail that most users never need to directly understand, but the consequence is that if you want to do any kind of high fidelity coupled optimziations (aero-structural, aero-propulsive, aero-thermal) with more than one PDE solver in the loop then OpenMDAO's architecture is going to be by far the most effective.
However, OpenMDAO does not offer a GUI. It does not have the same level of data tracking and visualization tools. Also, I know that mode-frontier offers the ability to split a single model up across multiple computers distributed across an organization. Mode Frontier, along with other tools like ModelCenter and Isight, all offer this kind of smooth user experience and code-free interaction that many find valuable.
Honestly, I'm not sure a direct comparison is really warranted. I think if you have an organization that invests in a commercial integration tool like Mode Fronteir, then you can still use OpenMDAO to create tightly coupled integrated optimizations which you can then include as boxes inside your overall integration framework.
You certainly can use OpenMDAO as a complete integration framework, and it has some advantages in that area related to derivatives and execution in distributed memory environments. But you don't have to, and it certainly does not have to be an exclusive decision.
Is there a way to get the IIS from Gurobi if I use it via the minizinc interface (i.e., mzn-gurobi) ?
Thanks,
Ofer
Currently no such option exists for mzn-gurobi. All available options can be seen by checking the help output: mzn-gurobi -h. Generally the options are for linear solvers (CBC, CPLEX, Gurobi) are shared. If you are missing this functionality, I would suggest making a feature request on the MiniZinc repository. (Note that this functionality wouldn't be able to point to the constraints in the MiniZinc model, only the generated FlatZinc constraints)
What is in development within MiniZinc are Minimal Unsatisfiable Sets, which in my understanding are the same. A special kind of MiniZinc solver is in development that will give a subset of constraints, in MiniZinc, that violate a model. Although it seems development is going strong, it might be a while before this program will be released. If you have an immediate need for such a tool, you can try contacting the MiniZinc Team.
I build up a optimization model in ojalgo (ExpressionsBasedModel). Is there a way to export it to check the model? So far I am only able to export the lower and upper limits of variables and constraints but I am not able to export the variable's coefficients of constraints. I checked the available functions but I coudn't find an appropriate one. Only importing an MPS file I could find. Has someone a hint how to export the model without using an extra framework/external libraries?
There is no way to generate/export an MPS file using ojAlgo.
If you want to verify solver results with some 3:d party solver, you can do that. I believe the community (free) version of cplex allows up to 1000 variables and constraints.
https://github.com/optimatika/ojAlgo-extensions/tree/master/ojAlgo-cplex
Does CVC4 an option to maximize or minimize the result model for bitvectors as Z3 does?
Thanks.
Unfortunately, CVC4 does not (yet) support optimization. For bitvectors, you can always do it yourself using multiple queries and binary search, but it's not built-in.
I would like to optimize a design by having an optimizer make changes to a CAD file, which is then analyzed in FEM, and the results fed back into the optimizer to make changes on the design based on the FEM, until the solution converges to an optimum (mass, stiffness, else).
This is what I envision:
create a blueprint of the part in a CAD software (e.g. CATIA).
run an optimizer code (e.g. fmincon) from within a programming language (e.g. Python). The parameters of the optimizer are parameters of the CAD model (angles, lengths, thicknesses, etc.).
the optimizer evaluates a certain design (parameter set). The programming language calls the CAD software and modifies the design accordingly.
the programming language extracts some information (e.g. mass).
then the programming language extracts a STEP file and passes it a FEA solver (e.g. Abaqus) where a predefined analysis is performed.
the programming language reads the results (e.g. max van Mises stress).
the results from CAD and FEM (e.g. mass and stress) are fed to the optimizer, which changes the design accordingly.
until it converges.
I know this exists from within a closed architecture (e.g. isight), but I want to use an open architecture where the optimizer is called from within an open programming language (ideally Python).
So finally, here are my questions:
Can it be done, as I described it or else?
References, tutorials please?
Which softwares do you recommend, for programming, CAD and FEM?
Yes, it can be done. What you're describing is a small parametric structural sizing multidisciplinary optimization (MDO) environment. Before you even begin coding up the tools or environment, I suggest doing some preliminary work on a few areas
Carefully formulate the minimization problem (minimize f(x), where x is a vector containing ... variables, subject to ... constraints, etc.)
Survey and identify individual tools of interest
How would each tool work? Input variables? Output variables?
Outline in a Design Structure Matrix (a.k.a. N^2 diagram) how the tools will feed information (variables) to each other
What optimizer is best suited to your problem (MDF?)
Identify suitable convergence tolerance(s)
Once the above steps are taken, I would then start to think MDO implementation details. Python, while not the fastest language, would be an ideal environment because there are many tools that were built in Python to solve MDO problems like the one you have and the low development time. I suggest going with the following packages
OpenMDAO (http://openmdao.org/): a modern MDO platform written by NASA Glenn Research Center. The tutorials do a good job of getting you started. Note that each "discipline" in the Sellar problem, the 2nd problem in the tutorial, would include a call to your tool(s) instead of a closed-form equation. As long as you follow OpenMDAO's class framework, it does not care what each discipline is and treats it as a black-box; it doesn't care what goes on in-between an input and an output.
Scipy and numpy: two scientific and numerical optimization packages
I don't know what software you have access to, but here are a few tool-related tips to help you in your tool survey and identification:
Abaqus has a Python API (http://www.maths.cam.ac.uk/computing/software/abaqus_docs/docs/v6.12/pdf_books/SCRIPT_USER.pdf)
If you need to use a program that does not have an API, you can automate the GUI using Python's win32com or Pywinauto (GUI automation) package
For FEM/FEA, I used both MSC PATRAN and MSC NASTRAN on previous projects since they have command-line interfaces (read: easy to interface with via Python)
HyperSizer also has a Python API
Install Pythonxy (https://code.google.com/p/pythonxy/) and use the Spyder Python IDE (included)
CATIA can be automated using win32com (quick Google search on how to do it: http://code.activestate.com/recipes/347243-automate-catia-v5-with-python-and-pywin32/)
Note: to give you some sort of development time-frame, what you're asking will probably take at least two weeks to develop.
I hope this helps.