We compared well known measurement methods for LogGP parameters and discuss their accuracy and network contention. Based on this, a new theoretically exact measurement method that does not saturate the network is derived and explained in detail. The applicability of our method is shown for the low level communication API of Open MPI across several interconnection networks. Based on the LogGP model, we developed a low overhead packet scheduling algorithm. It can handle different types of interconnects with different characteristics. It is able to produce schedules which are very close to the optimum for both small and large messages. The efficiency of the algorithm for small messages is show for a Open MPI implementation. The implementation uses the LogGP benchmark to obtain the LogGP parameters of the available interconnects and can so adapt to any given system.

We compared well known measurement methods for LogGP parameters and discuss their accuracy and network contention. Based on this, a new theoretically exact measurement method that does not saturate the network is derived and explained in detail. The applicability of our method is shown for the low level communication API of Open MPI across several interconnection networks. Based on the LogGP model, we developed a low overhead packet scheduling algorithm. It can handle different types of interconnects with different characteristics. It is able to produce schedules which are very close to the optimum for both small and large messages. The efficiency of the algorithm for small messages is show for a Open MPI implementation. The implementation uses the LogGP benchmark to obtain the LogGP parameters of the available interconnects and can so adapt to any given system.

The MPI_Barrier-collective operation, as a part of the MPI-1.1 standard, is extremely important for all parallel applications using it. The latency of this operation increases the application run time and can not be overlaid. Thus, the whole MPI performance can be decreased by unsatisfactory barrier latency. The main goals of this work are to lower the barrier latency for InfiniBand networks by analyzing well known barrier algorithms with regards to their suitability within InfiniBand networks, to enhance the barrier operation by utilizing standard InfiniBand operations as much as possible, and to design a constant time barrier for InfiniBand with special hardware support. This partition into three main steps is retained throughout the whole thesis. The first part evaluates publicly known models and proposes a new more accurate model (LoP) for InfiniBand. All barrier algorithms are evaluated within the well known LogP and this new model. Two new algorithms which promise a better performance have been developed. A constant time barrier integrated into InfiniBand as well as a cheap separate barrier network is proposed in the hardware section. All results have been implemented inside the Open MPI framework. This work led to three new Open MPI collective modules. The first one implements different barrier algorithms which are dynamically benchmarked and selected during the startup phase to maximize the performance. The second one offers a special barrier implementation for InfiniBand with RDMA and performs up to 40% better than the best solution that has been published so far. The third implementation offers a constant time barrier in a separate network, leveraging commodity components, with a latency of only 2.5 microseconds. All components have their specialty and can be used to enhance the barrier performance significantly.

The MPI_Barrier-collective operation, as a part of the MPI-1.1 standard, is extremely important for all parallel applications using it. The latency of this operation increases the application run time and can not be overlaid. Thus, the whole MPI performance can be decreased by unsatisfactory barrier latency. The main goals of this work are to lower the barrier latency for InfiniBand networks by analyzing well known barrier algorithms with regards to their suitability within InfiniBand networks, to enhance the barrier operation by utilizing standard InfiniBand operations as much as possible, and to design a constant time barrier for InfiniBand with special hardware support. This partition into three main steps is retained throughout the whole thesis. The first part evaluates publicly known models and proposes a new more accurate model (LoP) for InfiniBand. All barrier algorithms are evaluated within the well known LogP and this new model. Two new algorithms which promise a better performance have been developed. A constant time barrier integrated into InfiniBand as well as a cheap separate barrier network is proposed in the hardware section. All results have been implemented inside the Open MPI framework. This work led to three new Open MPI collective modules. The first one implements different barrier algorithms which are dynamically benchmarked and selected during the startup phase to maximize the performance. The second one offers a special barrier implementation for InfiniBand with RDMA and performs up to 40% better than the best solution that has been published so far. The third implementation offers a constant time barrier in a separate network, leveraging commodity components, with a latency of only 2.5 microseconds. All components have their specialty and can be used to enhance the barrier performance significantly.