Los Alamos National LaboratoryCrossroads
A critical element for improved predictive capability.

Crossroads computer

Moving forward by allowing applications to fully explore and exploit upcoming technologies

As the Nation’s nuclear stockpile moves further from the nuclear test base due to aging, remanufactured components, and Life Extension Programs (LEP), the need for predictive weapon calculations is becoming increasingly urgent. Crossroads, the third Advanced Technology (AT) system in the Advanced Simulation and Computing (ASC) Program, will be critical to the success of the National Nuclear Security Administration (NNSA) Stockpile Stewardship Program (SSP) and the current and planned LEP activities. The primary users of ASC platforms are designers, analysts, and computational scientists.

In 2020, the first AT system, Trinity, will be nearing the end of its useful lifetime. Crossroads is a Trinity replacement, a tri-lab computing resource for existing simulation codes, and a larger resource for ever-increasing computing requirements to support the weapons program. Crossroads will provide a large portion of the AT system resources for the NNSA ASC tri-lab simulation community: Lawrence Livermore National Laboratory (LLNL), Los Alamos National Laboratory (LANL), and Sandia National Laboratories (SNL), during the FY21-25 timeframe.

In addition to meeting NNSA Defense Programs’ mission needs, the architecture of Crossroads will keep ASC moving forward by allowing applications to fully explore and exploit upcoming technologies. These new technologies include processors, memory, input/output (I/O), interconnect, power efficiency, and reliability. Some of the largest and most demanding capability-class jobs will be able to run on Crossroads. These capabilities are required for supporting stockpile stewardship certification and assessments to ensure that the Nation’s nuclear stockpile is safe, secure, and reliable.

Crossroads will establish a validated predictive capability for key physical phenomena, quantifying and aggregating uncertainties in simulation tools, and providing mission-responsive computational environments. Simulation fidelity improvements include:

  • Physics fidelity—replacing calibrations with physics models to improve confidence of extrapolation away from the nuclear test base;
  • Numerical fidelity—Significant Finding Investigations (SFIs) are sensitive to fine scale 3D features, requiring much finer resolution; and
  • Geometric fidelity—neglected features need to be included; many are inherently 3D.

Crossroads will continue to push the cutting edge of what is possible on current systems with its' 3D simulations capabilities. By 2020, the goal of running high-resolution 3D simulations with full physics and geometric features will be attainable. Ultimately, Crossroads will accelerate industry’s R&D technology roadmap for the ASC program’s future exascale-class computational needs.

Alliance for Application Performance at Extreme Scale (APEX) is a collaboration between the Alliance for Computing at Extreme Scale (ACES) collaboration of Los Alamos National Laboratory (LANL) and Sandia National Laboratories (SNL) and the National Energy Research Scientific Computing Center (NERSC).Crossroads will be one of two systems procured by APEX.

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