Lawrence Livermore National Laboratory



ASC Sequoia—Advancing Technology for Uncertainty Quantification and Science at Scale

Ranked one of the world's most powerful computing system, Sequoia delivers the required petascale capabilities necessary to ensure the continued safety and reliability of the nation's aging nuclear deterrent. As the latest system from the long-term partnership between LLNL and IBM, Sequoia is a national asset and multi-national-laboratory resource.

The 20-petaFLOP/s Sequoia system has two main National Nuclear Security Administration missions, both of which require "predictive simulation" of complex systems. Predictive simulation is not just computing the behavior of a complex system (the results), but also generating a precise quantification of the uncertainty associated with the results. This is analogous to the "margin of error" cited in scientific and technical papers or commonly used to qualify poll or survey results. Achieving predictive simulation is critical to resolving scientific problems when validation by physical experiment (for example, underground nuclear testing) is impossible, impractical, or prohibited by law or treaty. Predictive simulation is necessary to sustain the nation's shrinking nuclear deterrent into the future as the deterrent continues to age. Sequoia's two missions are to:

  • Quantify the uncertainties in numerical simulations of nuclear weapons performance. This will require the execution of vast suites of simulations not possible on current systems.
  • Perform the advanced weapons science calculations needed to develop the accurate physics-based models for weapons codes.

Sequoia is primarily water cooled. Though orders of magnitude more powerful than such predecessor systems as ASC Purple and BlueGene/L, Sequoia is roughly 90 times more power efficient than Purple and about eight times more than BlueGene/L relative to the peak speeds of these systems. For systems of this scale, energy efficiency is of central importance and absolutely essential to drive down operating costs.


ASC Sequoia—the 20 petaFLOP/s, third-generation
IBM BlueGene system—in production at LLNL.
Sequoia Statistics
20 PF/s peak
1.5 PB memory; 4 PB/s bandwidth
1.5 M cores
3 PB/s link bandwidth
60 TB/s bisection bandwidth
0.5–1.0 TB/s Lustre bandwidth
55-PB disk
9.6 MW power, 4,000 ft2


Sequoia packaging hierarchy focuses on
simplicity and low power consumption.

Sequoia Archive