Erlkönig: Z (ζωιον) Past Status Entries

2004-01-21 Morphable X Servers

xvfbtex showing the xgltex server mapped onto an animated sinusoidal surface. Xterm shows ps output

Substantial tweaking has produced a version of xvfbtex with full tracking of the textured X server's cursor by user control of the pointer across the scene. Basically this means that when you move the mouse across a scene of objects, your path across the object with an X server framebuffer textured across the side will be tracked by that X server's pointer.

Currently pointer tracking is a special case, and has not yet been encapsulated in a form suitable for reuse, but that encapsulation will provide, among other things, a straightforward approach to interactive painting onto 3d surfaces.

2003-10 Ah, threads.

(Download the threaded life project)

I knew that writing the classic life cellular automaton as a orgy of gratuitous threads, one per cell, plus threads for input and display, would expose some limitations; that was the point. But I was surprised to discover just how much misinformation is out there about limits on the maximum number of threads in a process. So, to help anyone else trying to run a few thousand threads in one program: the cumulative stack size in all your threads is probably the problem. You can test this as easily as using the ulimit shell builtin to reduce your default stack size, and then seeing if suddenly your program can create more threads than before. The same reduction can be coded using pthread_attr_{get/set}stacksize(). With this method, I reduced the stack sizes for the cell threads in the test code from 1 MB to 1 KB for all but 3 threads, and now it works fine at 7103 threads instead of the earlier 234. The file /proc/sys/kernel/threads-max on my machine contains the value of 14336, suggesting a maximum of about twice what I'm seeing, but I don't see a need for anywhere near even what my testcase is using (although, I wonder if you could overlap the stacks if your threads used no variables or function calls...hehe). Good luck :-)