Introduction to Discrete-Event Simulation and the SimPy ... - matloff

(Note that if a Python name begins with , you must explicitly ask for access; the wildcard form of
from...import... doesn’t pick up such variables.)
SimPy has another way to keep track of simulated time (and other things), to be discussed in Section B.7.
B.4 Starting Over
During your debugging process, you will often need to start the program over again, even though you have
not finished. To do this, first stop the simulation, by calling the following SimPy function:
(Pdb) stopSimulation()
Then hit c a couple of times to continue, which will restart the program.
If your program runs into an execution error, hit c in this case as well.
The actions for other debuggers are similar; the key is the call to stopSimulation().
B.5 Repeatability
The debugging process will be much easier if it is repeatable, i.e. if successive runs of the program give
the same output. In order to have this occur, you need to use random.Random() to initialize the seed for
Python’s random number generator, as we have done in our examples here.
B.6 Peeking at the SimPy’s Internal Event List
Here is another trick which you may find useful. You can enable looking at SimPy’s internal event list by
placing the following code in each of your PEMs:
from SimPy.Simulation import _e
The internal events list is e.events, and is implemented as a Python dictionary type, showing the events
(address of threads) for each simulated time in the future. For example,
(Pdb) _e.events
{4.9862113069200458: [], 3.3343289782218619: []}
To do this effectively, code something like the following:
class Globals:
e = None # copy of the pointer SimPy.Simulation._e
...
def main():
...
initialize()
from SimPy.Simulation import _e
Globals.e = _e
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