Monte Carlo algorithms for computing neutral particle transport in plasmas have been vectorized and macrotasked. The techniques used are directly applicable to Monte Carlo calculations of neutron and photon transport, and Monte Carlo integration schemes in general. A highly vectorized code was achieved by calculating test flight trajectories in loops over arrays of flight data, isolating the conditional branches to as few a number of loops as possible. A number of solutionis are discussed to the problem of gaps appearing in the arrays due to completed flights, which impede vectorization. A simple and effective implementation of macrotasking is achieved by dividing the calculation of the test flight profile among several processors. A tree of random numbers is used to ensure reproducible results. The additional memory required for each task may preclude using a large number of tasks. In future machines, the limit of macrotasking may be possible, with each teat flight, and split test flight, being a separate task. DISCLAIMER T»>is report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Governir -it nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsi bility lor the accuracy, completeness, or usefulness of ar.y ioformatioti. apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its eodoracmcat, recom mendation, or favoring by the United Slates Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect thoie or the Ui.ited States Government or any agency thereof-
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