As a part of my masters thesis I am programming an external C-Subroutine for a MBS-Software in order to work as a force element like e.g.:
force=subfunction(displacement)
There is a Matlab code doing this and very time-consuming to implement it in C.
So the following options I considered to overcome this the most efficient way:
1. Using Matlab-Compiler to create a .exe and start it from C
Very nice and easy solution. However the problem is that the mbs-solver calls the function >10000 times and the compiled Matlab executable has to load the MCR (Matlab Compiler Runtime) every single time! The processing time is very short (~0.001 seconds) but the loading of MCR takes about 5 seconds (!) for each iteration step. This makes this option unfortunately useless for me.
http://www.mathworks.de/support/solutions/en/data/1-1ARNS/
"Every time you start a compiled executable, you essentially start another instance of MATLAB."
2. Using Matlab-Compiler to create a shared library etc.
I haven't tried this. As far as I researched I understood that also for these options the MCR has to be started every single step like the option 1.
3. Using the Matlab-Coder to generate a C-Code
It's not an easy option as far as I tried sometimes. The generated code should be optimized. Would it really be more efficient?
4. Starting Matlab-Executable only the first time without closing it and communicating the C-Code over any files
Just a conception: I would like to start Matlab-Exe. in the first iteration step and let write a file which contents "displacement". Then I would scan every milisecond the file from Matlab if any new value came. I would process it and write in another file and the C-Routine that scans the result file every milisecond would find the new value and keep working.
I can imagine that this works faster but surely it's bit tricky to implement until it works bugfree.
I am thankful for any reports about your experiences or ideas.
To offer a couple options not yet listed:
If you use SAGE, you can call both MATLAB and C code from a single script. You may have to wrap the C code in Cython, but this is quite easy. You technically wouldn't be calling the MATLAB from the C, but rather the MATLAB and C both from a third script, but the result would be the same.
If you're willing to translate the MATLAB into a very-similar Numpy script, you could use Cython to compile the complex code and integrate it all very cleanly. I've done these translations several times and it's a pretty painless process.