Understanding the measured performance of parallel applications in real systems is difficult—with the aim to utilize the resources available, optimizations deployed in hardware and software layers build up to complex systems. However, in order to identify bottlenecks the performance must be assessed. This paper introduces PIOsimHD, an event-driven simulator for MPI-IO applications and the underlying (heterogeneous) cluster computers. With the help of the simulator runs of MPI-IO applications can be conducted in-silico; this includes detailed simulation of collective communication patterns as well as simulation of parallel I/O. The simulation estimates upper bounds for expected performance and helps assessing observed performance.Together with HDTrace, an environment which allows tracing the behavior of MPI programs and internals of MPI and PVFS, PIOsimHD enables us to localize inefficiencies, to conduct research on optimizations for communication algorithms, and to evaluate arbitrary and future systems. In this paper the simulator is introduced and an excerpt of the conducted validation is presented, which demonstrates the accuracy of the models for our cluster.

@article{SPPOAASLK12,
	author	 = {Julian Kunkel},
	title	 = {{Simulating parallel programs on application and system level}},
	year	 = {2012},
	month	 = {06},
	publisher	 = {Springer},
	address	 = {Berlin, Heidelberg},
	journal	 = {Computer Science -- Research and Development},
	series	 = {Volume 28 Number 2-3},
	issn	 = {1865-2042},
	doi	 = {http://dx.doi.org/10.1007/s00450-012-0208-2},
	abstract	 = {Understanding the measured performance of parallel applications in real systems is
      difficult—with the aim to utilize the resources available, optimizations deployed in hardware
      and software layers build up to complex systems. However, in order to identify bottlenecks the
      performance must be assessed. This paper introduces PIOsimHD, an event-driven simulator for
      MPI-IO applications and the underlying (heterogeneous) cluster computers. With the help of the
      simulator runs of MPI-IO applications can be conducted in-silico; this includes detailed
      simulation of collective communication patterns as well as simulation of parallel I/O. The
      simulation estimates upper bounds for expected performance and helps assessing observed
      performance.Together with HDTrace, an environment which allows tracing the behavior of MPI
      programs and internals of MPI and PVFS, PIOsimHD enables us to localize inefficiencies, to
      conduct research on optimizations for communication algorithms, and to evaluate arbitrary and
      future systems. In this paper the simulator is introduced and an excerpt of the conducted
      validation is presented, which demonstrates the accuracy of the models for our cluster.},
	url	 = {http://link.springer.com/article/10.1007/s00450-012-0208-2},
}