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SNAP serves as a proxy application to model the performance of a modern discrete ordinates neutral particle transport application. SNAP may be considered an update to Sweep3D, intended for hybrid computing architectures. It is modeled off the Los Alamos National Laboratory code PARTISN. PARTISN solves the linear Boltzmann transport equation (TE), a governing equation for determining the number of neutral particles (e.g., neutrons and gamma rays) in a multi-dimensional phase space. SNAP itself is not a particle transport application; SNAP incorporates no actual physics in its available data, nor does it use numerical operators specifically designed for particle transport. Rather, SNAP mimics the computational workload, memory requirements, and communication patterns of PARTISN. The equation it solves has been composed to use the same number of operations, use the same data layout, and load elements of the arrays in approximately the same order. Although the equation SNAP solves looks similar to the TE, it has no real world relevance.

Required Problem Sets

For SNAP, small, medium, large, extra-large and grand challenge problems have been defined. See the README.APEX file in the source distribution details. The extra-large definition will be used as the reference problem and the grand challenge definition is the target problem in the calculation of SSI.

Source Distribution

Source and problem definitions can be downloaded here.

How to Build, Run and Verify

Refer to the README.APEX file in the source distribution.


SNAP was developed at Los Alamos National Laboratory Richard P. Feynman Center for Innovation.

Change Log


Updated source distribution. README.APEX now states to use "Grind Time" as the figure of merit. Failed to do this on the 5/10/2016 update. There are no other changes.


Updated source distribution to LANL release version 1.07
-- See snap_release_v1.07.txt in the distribution
Now using Grind Time as the figure of merit

12/21/2015 Source distribution link created
10/30/2015 Initial release