Scalability of parallel applications depends on a number of characteristics, among which is eﬃcient communication, equal distribution of work or eﬃcient data lay-out. Especially for methods based on domain decomposition, as it is standard for, e.g., molecular dynamics, dissipative particle dynamics or particle-in-cell methods, unequal load is to be expected for cases where particles are not distributed homogeneously, diﬀerent costs of interaction calculations are present or heterogeneous architectures are invoked, to name a few. For these scenarios the code has to decide how to redistribute the work among processes according to a work sharing protocol or to dynamically adjust computational domains, to balance the workload.
The seminar will provide an overview about motivation, ideas for various methods and implementations on the level of tensor product decomposition, staggered grids, non-homogeneous mesh decomposition and a recently developed phase ﬁeld approach. An implementation of several methods into the load balancing library ALL, which has been developed in the Centre of Excellence E-CAM, is presented. A use case is shown for the Materials Point Method (MPM), which is an Euler-Lagrange method for materials simulations on the macroscopic level, solving continuous materials equations.
The seminar is organised in three main parts:
- Overview of Load Balancing
- The ALL Load Balancing Library
- Balancing the Materials Point Method with ALL