A Communication Model for Small Messages with InfiniBand

Designing new and optimal algorithms for a specific architecture requires accurate modelling of this architecture. This is especially needed to choose one out of different solutions for the same problem or to proof a lower bound to a problem. Assumed that the model is highly accurate, a given algorithm can be seen as optimal solution if it reaches the lower bound. Therefore the accuracy of a model is extremely important for algorithmic design. A detailed model can also help to understand the architectural details and their influence on the running time of different solutions and it can be used to derive better algorithms for a given problem. This work introduces some architectural specialities of the InfiniBand network and shows that most widely used models introduce inaccuracies for sending small messages with InfiniBand. Therefore a comparative model analysis is performed to find the most accurate model for InfiniBand. Basing on this analysis and a description of the architectural specialities of InfiniBand, a new, more accurate but also much complexer model called LoP is deduced from the LogP which can be used to assess the running time of different algorithms. The newly developed model can be used to find lower bounds for algorithmic problems and to enhance several algorithms.