Java bridge

This library depends on the Python-to-Java bridge JPype. It therefore inherits its limitation, in that only one Java virtual machine can be managed within the same Python session, and thus only one Comsol client. If several simulations are to be run in parallel, distributed over independent processor cores in an effort to achieve maximum speed-up of a parameter sweep, they have to be started as separate Python (sub-)processes. This is a feasible work-around, but a limitation nonetheless.

For the same reason, the unit tests that come with MPh fail when collected and run via the testing framework pyTest. They must be run directly from the command line. Since they cannot be used for continuous integration testing anyway, given that they depend on Comsol being installed on the local machine, this is but a minor inconvenience.

Furthermore, there are some known, but unresolved issues with JPype’s shutdown of the Java virtual machine. Most notably, pressing Ctrl+C to interrupt an ongoing operation will usually crash the entire Python session. So do not rely on that to work.

(There is an alternative Java bridge, pyJNIus, which is not limited to one virtual machine, but then fails in another regard: A number of Java methods exposed by Comsol are inexplicably missing from the Python encapsulation.)

Creating models

The API is intentionally scope-limited to automating the simulation workflow, such as running parameter sweeps or optimization routines with customized, Python-powered post-processing. Exposing any and all Comsol features to create or alter every aspect of a model, and thus replicating the entire Java API, albeit in a more pythonic way, is out of scope.

Though users who do want to dig deeper may access the “pythonized” Java layer directly, via the .java attribute of Client instances (mapping to Comsol’s ModelUtil) as well as Model (mapping to Comsol’s model). Refer to Comsol’s programming manual for details.

This might even be worthwhile for Java developers of Comsol applications, as the interactive Python prompt provides easy introspection of the object hierarchy. In these circumstances, one might find the convenience function mph.inspect helpful, as it not only lists an object’s methods in a more readable way than Python’s built-in dir, but also displays the “properties” possibly defined on a model node.

In that event, it may equally help to call the returned Python model object something like pymodel and assign the name model to Then you can just copy-and-paste Java (or even Matlab) code from the Comsol Programming Manual or as exported from the Comsol front-end. Python will gracefully overlook gratuitous semicolons at the end of statements, so this approach would even work for entire blocks of code. Keep in mind, however, that JPype cannot perform all type conversions silently in the background. Occasionally, when there is ambiguity in overloaded methods, you will have to cast types explicitly. Refer to the JPype documentation for help.

Client-server mode

In addition to running a stand-alone Comsol client, MPh also supports client–server connections. Client and server may either run on the same machine (which may or may not have benefits in terms of memory overhead) or they may communicate across the network. Note, however, that the latter scenario has never actually been tested — for lack of a network license required for that purpose. It may work as is, or may require transmitting login details: user name and password. File a GitHub issue if you are in a position to test this and want the problem solved.

Linux support

On Linux, the stand-alone Comsol client (as opposed to a client connecting to a server) will fail to start if all you did was install MPh. You will also have to add the names of shared-library folders to the environment variable LD_LIBRARY_PATH and explicitly export it. Otherwise initialization of the stand-alone client will throw a java.lang.UnsatisfiedLinkError because required external libraries cannot be found.

Add the following lines at the end of your shell configuration file, such as .bashrc:


Clearly, these paths depend on the installed Comsol version and will have to be adapted accordingly.

Requiring this variable to be set correctly limits the possibility of selecting a specific back-end from within MPh, as adding multiple installations to that search path would very likely lead to name collisions. Ideally, starting a stand-alone client would work out of the box, without the above manual configuration. However, this issue is currently unresolved.

macOS support

Support for macOS is experimental and entirely untested. The implementation is nearly identical to the one for Linux, and only deviates wherever the Comsol documentation indicates a difference in naming. As such, the environment variable for the library search path is instead called DYLD_LIBRARY_PATH, and Comsol would typically be found in, e.g., /Applications/COMSOL56/Multiphysics. Adjust your shell configuration accordingly. And please report back on the corresponding Github issue if you were able to test this.