WRENCH Simulation of Work Queue

Our colleagues Henri Casanova (U Hawaii) and Rafael Ferreira da Silva (USC), along with their students, have recently published a paper highlighting their work in the WRENCH project.  The have constructed a series of simulators have model the behavior of distributed systems, for the purposes of both performance prediction and education.

In their paper " Developing accurate and scalable simulators of production workflow management systems with WRENCH " the describe simulators that correspond the the Pegasus workflow management system and our own Work Queue distributed execution framework.

Of course, any simulation is an imperfect approximation of a real system, but what's interesting about the WRENCH simulations is that they allow us to verify the basic assumptions and behavior of a software implementation.  In this example, the real system and the simulation show the same overall behavior, except that the real system has a stair-step behavior:

So, does that mean the simulation is "wrong"?  Not really!  In this case, the software is showing an undesirable behavior that is due either to incorrect logging or possibly a convoy effect.  In short, the simulation helps us to find a bug relative to the "ideal" design.  Nice!