Parallel Implementation of Adaptive Spacetime Simulations A Parallel Implementation of Adaptive Spacetime Simulations A. Becker and L. V. Kale, Department of Computer Science Objective: As multi-core processors become ubiquitous and supercomputers grow ever faster, parallel programs allow scientists to apply massive computational power to their problems. Serial implementations of adaptive spacetime solution methods deliver unprecedented resolution for multi- scale problems; parallel implementations promise exciting breakthroughs in our ability to simulate materials physics. We are developing new software infrastructure to realize this potential. However, the asynchronous character of the method and highly dynamic mesh refinement pose significant challenges. Approach: We implement our adaptive spacetime meshing algorithm in ParFUM, a general framework for parallel finite element programs. ParFUM handles the communication and synchronization needed to divide the mesh across hundreds or thousands of processors while managing adaptive mesh operations. Impact: Spacetime multiscale simulations can take days on a single processor. By running simulations in parallel on supercomputers, we can reduce execution times to hours or minutes, allowing scientists to study problems of much greater physical complexity. Left: Spacetime finite element mesh of crack-tip wave scattering. Vertical axis represents time; horizontal axes represent space. The propagation of shock waves is readily apparent from the pattern of adaptive mesh refinement. Below: We decompose the space mesh into ‘chunks’ distributed across many processors. Adaptive mesh refinement and coarsening operations must operate across chunk boundaries (shown as heavy lines). Boundaries must be adjusted and chunks redistributed to minimize communication and balance the load between the processors. Website: http://www.cpsd.uiuc.edu/