I've found that under some circumstances the Eclipse python debugger can be unreliable. For example, when stepping through a memory-hungry Python program I've found that after a certain point the debugger fails to respond. The entire process hangs with 100% cpu load.
I've heard (unconfirmed) reports from developers that when this occurs it might actually not be a hang but very slow, for example a step which usually takes a micro-second might be taking five minutes.
I've observed this with both the regular eclipse debugger (e.g. when you do debug as->python run) and the pydev network debugger. The point at which things stop working seems quite arbitrary but re-producable. I'm debugging purely numerical functions so there's no obvious socket or tcp activity which could disrupt a network debugger. Nevertheless, the point at which the failure occurs seems to be quite consistent for a given workstation & task.
I get almost exactly the same effect whether I debug using debug as->python run as I might if I use the pydev's network debugger ('import pydevd;pydevd.settrace()') - where one fails the other is also likely to fail.
If I were to run the script normally (no debugger) it executes without any hangs. Furthermore, if I replace the eclipse debugger with the old-skool inline break-point ('import pdb;pdb.set_trace()') everything works just fine. Pdb almost never goes wrong, however there are times I simply cannot use it, for example when I am debugging a python function invoked from Excel - as there is no console present.
I've noticed that this failure never seems to occur with trivial programs, hence I've tentatively concluded that the fault may be memory related.
So - is anybody aware of what might be causing this unreliability. Are there any tweaks I can make to the debugger or environment that might make the debugger work more reliably?
FYI, running Python 2.4.4 on Windows XP 32bit with the latest Eclipse & Pydev. Psyco (JIT Compiler) is not available.