An Overview of ASC Efforts in Parallel First-Order Sn Methods

The cessation of nuclear testing in the United States during the 1990’s created an increased need for improvements in other tools used to maintain the stockpile. The Accelerated Strategic Computing Initiative (ASCI) was created to address a broad range of computational challenges at the U.S. weapons laboratories, encompassing both hardware and software. Algorithmic improvements were sought in a variety of computational disciplines, including radiation transport. One transport approach targeted for improvements is the method of discrete ordinates (Sn) as applied to the first-order form of the Boltzmann transport equation, in particular for parallel computations on unstructured meshes. The purpose of this paper is to survey the research into parallel first-order Sn methods performed within the ASCI program.