D.2 Shared library problems

D.2.1 Startup Time

Start up time of a binary that uses shared libraries is increased. We believe that some of the increased startup time comes from running star constructors. We are working on modifying Ptolemy so that startup time of binaries that use shared libraries is decreased. See "Startup Time" below for more information.
The time necessary to start up a debugger is sometimes increased. When the debugger starts up, it usually has to load all the shared libraries so that the debugger knows where to find symbols.
Building is more complex. Unfortunately, shared libraries are very architecture dependent. Also, the commands and command line arguments differ between architectures. Finally, how different versions of the same shared library are handled, along with the shared library naming conventions also vary between architectures.
You need to keep track of where the shared libraries are, either by using RPATH at link time or setting LD_LIBRARY_PATH or SHLIB_PATH. The problem is that if you are building a C Code Generation (CGC) application that uses shared libraries, then at runtime the user needs to either have the necessary shared libraries in their LD_LIBRARY_PATH or SHLIB_PATH, or the binary needs to have the RPATH to the shared libraries encoded into it. This can be done with an option of the linker. The various commands to do this are architecture dependent, and Default-CGC target usually fails. The Makefile_C target and the TclTk_Target which is derived from Makefile_C is much more likely to work with shared libraries.
It could be the case that binaries that use shared libraries might use slightly more memory.

D.2.1 Startup Time

In Ptolemy you can build a pigiRpc that has only the domains you are interested in with Jose Pino's mkPtolemyTree script in $PTOLEMY/bin, see the Programmer's Manual for more information. The startup time for a full pigiRpc is greater than for a pigiRpc.ptrim (SDF, DE, CGC and a few other small domains). If you use either pigiRpc.ptrim or pigiRpc.ptiny (SDF and DE only), then the start up time is quite reasonable. If you regularly use some of the other less common domains, then you can build special pigiRpc with just your domains.

One reason that startup time is increased might be because Ptolemy constructs a lot of objects and processes many lists of things like domains. We may be able to decrease startup time by carefully managing the star constructors.

One way to speed things up might be to create a large shared library that has the domains in which you are interested. Startup time might be faster if everything is in one file. Currently we have about 80 different shared libraries.

Combining these libraries into a few big libraries for ptiny, ptrim and pigi binaries might help. Of course, we could leave the 80 libraries and just add the new libraries. We have not tried this, but it might be interesting.