Effective out-of-core parallel delaunay mesh refinement using off-the-shelf software

Abstract

We present three related out-of-core parallel mesh generation algorithms and their implementations for small size computational clusters. Computing out-of-core permits to solve larger problems than otherwise possible on the same hardware setup. Also, when using shared computing resources with high demand, a problem can take longer to compute in terms of wall-clock time when using an in-core algorithm on many nodes instead of using an out-of-core algorithm on few nodes. The difference is due to wait-in-queue delays that can grow exponentially to the number of requested nodes. In one specific case, using our best method and only 16 nodes it can take several times less wall-clock time to generate a 2 billion element mesh than to generate the same size mesh in-core with 121 nodes. Although our best out-of-core method exhibits unavoidable overheads (could be as low as 19% in some cases) over the corresponding in-core method (for mesh sizes that fit completely in-core), this is a modest and expected performance penalty. We evaluated our methods on traditional clusters of workstations as well as presented preliminary performance evaluation on emerging BlueWaters supercomputer.