Stack overflow/Mathematica

*To*: mathgroup at yoda.physics.unc.edu*Subject*: Stack overflow/Mathematica*From*: Scott Perkins <perkins at acs00.cc.vanderbilt.edu>*Date*: Fri, 8 May 92 11:30:24 CDT

>Date: Wed, 6 May 1992 09:52:07 -0500 >From: "Theodore W. Gray" <guam!me at wri.com> >To: perkins at acs00.cc.vanderbilt.edu >Subject: Stack overflow I don't know if you've gotten the response that I sent to Steve Christensen about stack overflow problems, but in case you don't I'll tell you directly..... You can set the stack size used by Mathematica: The Startup Preferences dialog (Preferences submenu in Edit menu) has a field where you can type in any stack size you like (the default is 512K). The new size takes effect when you restart Mathematica. The current scheme Mathematica uses to try to avoid stack overflow errors is the variable $RecursionLimit, by default 256. Evaluation will halt if recursion exceedes this depth. This is not a perfect scheme, because it assumes that the average stack frame is less than 2K, which is almost, but not always, true. Also, there are some cases where a function is internally recursive without incrementing the recursion depth counter. We have considered putting in an explicit check of stack usage in front of each recursive call, but there are serious problems with this. For one thing, it would slow everything down, particularly some things that you really want to be fast. For now, if you do have a crash caused by stack overflow, you can solve it by increasing the stack size. However, this is very rarely the actual cause of the trouble, since $RecursionLimit almost always protects you. I don't follow the netnews, so I don't know what's been said about Mathematica and System 7, but I can say the following things. There were two unrelated bugs, one in V2.0.3 (fixed in 2.0.4) and one in recent 2.1 beta versions (you mention being a beta site) which would cause crashes particularly under System 7. The first during rendering of 8-bit color graphics, and the other while switching back and forth repeatedly between applications. These have both been fixed, and neither exists in the currently shipping version. As for things Apple could or could not do to improve performance, there are a lot. For one thing, the virtual memory swapping speed in System 7 is very slow. For another, having to decide ahead of time how much memory to allow Mathematica to ever use tends to cause people to allot less memory that is going to be needed. If Mathematica could grow its partition as needed, you would be much less likely to run out of memory. Not that this excuses crashing on out of memory condition, which should never happen, but still it would make you much more likely to get an answer. (Even if we were all perfect superhumans, Mathematica would still not be able to give a correct answer without enough memory.) You are welcome to forward this to the newsgroup if you like: As I said I don't follow netnews, but someone from WRI will end up posting something similar. Theo