Hi Phil: You have probably noticed my recent push of commit 3da0c90. That commit contains my recent (fairly small amount of) wxwidgets IPC code progress. The unnamed semaphores method requires the shared memory buffer be a struct (so that the buffer contains room for the required semaphores as well as the data array). So all I have done so far is to adjust the IPC code so it can use a struct for the shared memory, but at least this commit tests without issues.
N.B. the new IPC code is only exercised if the experimental cmake option (which defaults to OFF) is set to ON using -DPL_HAVE_UNNAMED_POSIX_SEMAPHORES=ON. And conditional compilation will be used a lot for this development project. So for the Windows case the code that is compiled should be completely unaffected by any of my changes, and for the non-Windows case by default the OLD IPC method will be preserved and used unless and until the new IPC method for that case is at least as efficient and reliable as the old one. So in the ideal case (where all steps below ultimately work and there are no efficiency reductions due to any of these steps) the remainng planned steps in this development effort for the -DPL_HAVE_UNNAMED_POSIX_SEMAPHORES=ON case are as follows: 1. Make the current one-semaphore approach work with unnamed semaphores. The last commit put essentially all the infrastructure in place to support this further change so this change should be a simple matter of replacing (for this case) the calls to sem_open and sem_close with sem_init and sem_destroy, and the rest of the current one-semaphore code should work as is along with the mutex and sleep API calls required by this method. 2. Move from the present one-semaphore approach (which necessarily includes mutex and sleep activity) to the mutex- and sleep-free two-semaphore model following the cmake/test_linux_ipc proof-of-concept project. 3. Implement a two-semaphore version of (2) that uses named semaphores instead of unnamed semaphores (because not all POSIX systems support unnamed semaphores). So this version should differ from 2 only by a few lines of code (which are already conditionally in place) to use sem_open and sem_close rather than sem_init and sem_destroy. N.B. like (2) this approach should also not require any use of mutex or sleep API. 4. Implement a build system change to test for unnamed semaphore functionality and use approach (2) if that functionality is available but otherwise use approach (3). This should allow us to drop the present one-semaphore approach that is used in the non-Windows case. In sum, my work is cut out for me, but at least I have made some initial progress toward the above goals, and I am beginning to get a bit more comfortable with C++. Alan __________________________ Alan W. Irwin Astronomical research affiliation with Department of Physics and Astronomy, University of Victoria (astrowww.phys.uvic.ca). Programming affiliations with the FreeEOS equation-of-state implementation for stellar interiors (freeeos.sf.net); the Time Ephemerides project (timeephem.sf.net); PLplot scientific plotting software package (plplot.sf.net); the libLASi project (unifont.org/lasi); the Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project (lbproject.sf.net). __________________________ Linux-powered Science __________________________ ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot _______________________________________________ Plplot-devel mailing list Plplot-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/plplot-devel
