While multithreading is faster in some cases, sometimes we just want to spawn multiple worker processes to do work. This has the benefits of not crashing the main app if one of the worker crashes, and that the user doesn't need to worry a lot about inter-locking stuffs.
COM+'s Application Pooling seems like a good way to achieve this on Windows. The downside is that we need to write a COM+ wrapper for the worker process.
However, when I search for Application Pooling on Google, it seems like most of its usages are related to IIS. Don't other applications (such as scientific/graphics) find it useful to spawn multiple worker processes?
So there are several questions:
Why isn't COM+ more popular in areas other than IIS? If I write a non-IIS application and want to use process management on Windows, should I go with COM+ or are there better alternatives out there?
What would be the cross platform way to do it? Are there libraries out there that give me a "process pool" (worker processes will intelligently pick up work, can be managed, etc.)
I can't offer any answers to the COM aspect of your question, but it's worth noting there's another world (besides HPC MPI) where multi-processing (rather than the more common multi-threading approach) is apparently alive, well and thriving: Python.
Why ? Python's GIL ("global interpreter lock") cripples most attempts to multithread python code so badly that multiprocessing is the generally recommended approach to parallelising Python on SMP. The standard library includes process pools; there are various other options too.
Python certainly ought to satisfy any multi-platform requirement!