.. image:: images/sm_SimPy_Logo.png
   :align: left

=========================
 SimulationRTManual
=========================


:Authors: - Klaus Muller <Muller@users.sourceforge.net>
          - Tony Vignaux <Vignaux@users.sourceforge.net>

:Version:  1.0
:Date: 2003-December-18
:SimPy version: 1.4
:Web-site: http://simpy.sourceforge.net/
:Python-Version: 2.2, 2.3
:Created: 2003-December-18

----------------------------
 A Manual for SimulationRT
----------------------------
This manual describes SimulationRT, a SimPy module which supports
synchronizing the execution of simulation models with real (wallclock) time.

Acknowledgement
===============

SimulationRT is based on an idea by Geoff Jarrad of CSIRO (Australia). He
contributed a lot to its development and testing on Windows and Unix.

Introduction
============

SimulationRT allows synchronizing simulation time and real (wallclock) time. 
This capability can be used to implement e.g. interactive game applications or
to demonstrate a model's execution in real time.

Over and above
the capabilities provided by Simulation, SimulationStep caters for executing
SimPy models at user-controlled speed. This is done by setting a parameter
in the call to *simulateSimulationStep is a derivative of the Simulation module. It is identical to
Simulation, except for the *simulate* function which takes an additional parameter
controlling execution speed. 

Here is an example::

    ## RealTimeFireworks.py
    from __future__ import generators
    from SimPy.SimulationRT  import *
    from random import *
    import time
    class Launcher(Process):
        def launch(self):
            while True:
                print "Launch at %.1f; wallclock: %s"%(now(),time.clock()-startTime)
                yield hold,self,uniform(1,maxFlightTime)
		print "Boom!!! Aaaah!! at %.1f; wallclock: %s"%(now(),time.clock()-startTime)
    def model():
        initialize()
        for i in range(nrLaunchers):
            lau=Launcher()
            activate(lau,lau.launch())
        simulate(real_time=True,rel_speed=1,until=20) ##unit sim time = 1 sec clock
    nrLaunchers=2
    maxFlightTime=5.0 
    startTime=time.clock()
    model()
    
*rels_speed=1* sets the synchronization so that 1 simulation time unit
is executed approximately in 1 second wallclock time.
Run under Python 2.2.2 on a Windows XP-box (1.7 GHz), this output resulted
over about 18 seconds of wallclock time::

	Launch at 0.0; wallclock: 0.000195555580376
	Launch at 0.0; wallclock: 0.00190107960634
	Boom!!! Aaaah!! at 1.8; wallclock: 1.78082661344
	Launch at 1.8; wallclock: 1.78274501368
	Boom!!! Aaaah!! at 2.8; wallclock: 2.84245930698
	Launch at 2.8; wallclock: 2.84435982785
	Boom!!! Aaaah!! at 4.1; wallclock: 4.08443978215
	Launch at 4.1; wallclock: 4.09004328762
	Boom!!! Aaaah!! at 5.2; wallclock: 5.14561822801
	Launch at 5.2; wallclock: 5.14878203794
	Boom!!! Aaaah!! at 7.0; wallclock: 6.99845622838
	Launch at 7.0; wallclock: 7.00175357483
	Boom!!! Aaaah!! at 7.4; wallclock: 7.39919794276
	Launch at 7.4; wallclock: 7.40245282571
	Boom!!! Aaaah!! at 9.7; wallclock: 9.69250728794
	Launch at 9.7; wallclock: 9.69912935862
	Boom!!! Aaaah!! at 10.6; wallclock: 10.5938587167
	Launch at 10.6; wallclock: 10.6006140445
	Boom!!! Aaaah!! at 13.8; wallclock: 13.8082362423
	Launch at 13.8; wallclock: 13.8134877477
	Boom!!! Aaaah!! at 14.1; wallclock: 14.1385670525
	Launch at 14.1; wallclock: 14.1438146468
	Boom!!! Aaaah!! at 16.4; wallclock: 16.411963811
	Launch at 16.4; wallclock: 16.4172373863
	Boom!!! Aaaah!! at 17.1; wallclock: 17.1429980626
	Launch at 17.1; wallclock: 17.1482308506
	Boom!!! Aaaah!! at 18.1; wallclock: 18.0742063586
	Launch at 18.1; wallclock: 18.0794469688
	
Clearly, the wallclock time does not deviate significantly from the simulation time.

Limitations
============
This module works much better under Windows than under Unix or Linux, i.e., it gives
much closer synchronization.
Unfortunately, the handling of time in Python is not platform-independent at all.
Here is a quote from the documentation of the *time* module::

    "clock()
    On Unix, return the current processor time as a floating point number expressed in seconds. 
    The precision, and in fact the very definition of the meaning of ``processor time'' , depends 
    on that of the C function of the same name, but in any case, this is the function to use for 
    benchmarking Python or timing algorithms.

    On Windows, this function returns wall-clock seconds elapsed since the first call to this 
    function, as a floating point number, based on the Win32 function QueryPerformanceCounter(). 
    The resolution is typically better than one microsecond. 
    "


The SimulationRT API
======================

Structure
---------
Basically, SimulationStep has the same API as Simulation, but with
a change in the definition of simulate.

**simulate**
------------------

Executes the simulation model.

Call:

	**simulate(<optional parameters>)**

Mandatory parameters:
	None.

Optional parameters:
	- **until=0** : the maximum simulation (end) time (positive floating point number; default: 0)
	- **real_time=False** : flag to switch real time synchronization on or off (boolean; default: False, meaning no synchronization)
	- **rel_speed=1** : ratio simulation time over wallclock time; example: *rel_speed=200* executes 200 units of simulation time in about one second (positive floating point number; default: 1, i.e. 1 sec of simulation time is executed in about 1 sec of wallclock time)

Return value:
	Simulation status at exit.

	
$Revision: 1.0 $ $Date: 2004-05-15 11:09:27+02 $ kgm
