In late 2017, IBM will begin delivery of Sierra, the latest in a series of leading-edge Advanced Simulation and Computing (ASC) Program supercomputers. Delivering peak speeds of up to 150 petaflops (1015 floating-point operations per second), Sierra is projected to provide at least four to six times the performance of Sequoia, Livermore’s current flagship supercomputer. To run efficiently on Sierra, applications must be modified to achieve a level of task division and coordination well beyond what previous systems demanded.