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DOE OSTI2014

COMPOSE-HPC: Software Composition for Extreme Scale Computational Science and Engineering

Software composition is an important aspect of computational science software engineering due to large scale production science codes involving multiple programming languages, execution and concurrency models. To date, programmers must manage the complexity of building and maintaining such systems largely by hand with minimal (if any) automated assistance. As such, a great deal of programmer time is spent generating and maintaining code which leads to a high maintenance and development cost, as well as an increased risk of errors being introduced by hand than would be expected in an automated system. COMPOSE-HPC was a multi-institutional effort, with the Galois contribution focused on a specific area of code analysis and software infrastructure. Specifically, Galois led the design and implementation for the Parser for Annotations in a User-specified Language (PAUL), as well as collaborating with SNL and LLNL on the Retargetable Open Transformation Engine (ROTE). Both components were built on top of the ROSE compiler infrastructure from LLNL. All artifacts developed under the COMPOSE-HPC program are available on the github.com and sourceforge.net open source hosting sites under permissive BSD3 software licenses.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2022

Multinode Multi-GPU Two-Electron Integrals: Code Generation Using the Regent Language

The computation of two-electron repulsion integrals (ERIs) is often the most expensive step of integral-direct self-consistent field methods. Formally it scales as O(N 4 ), where N is the number of Gaussian basis functions used to represent the molecular wave function. In practice, this scaling can be reduced to O(N 2 ) or less by neglecting small integrals with screening methods. The contributions of the ERIs to the Fock matrix are of Coulomb (J) and exchange (K) type and require separate algorithms to compute matrix elements efficiently. We previously implemented highly efficient GPU-accelerated J-matrix and K-matrix algorithms in the electronic structure code TeraChem. Although these implementations supported the use of multiple GPUs on a node, they did not support the use of multiple nodes. This presents a key bottleneck to cutting-edge ab initio simulations of large systems, e.g., excited state dynamics of photoactive proteins. We present our implementation of multinode multi-GPU J- and K-matrix algorithms in TeraChem using the Regent programming language. Regent directly supports distributed computation in a task-based model and can generate code for a variety of architectures, including NVIDIA GPUs. We demonstrate multinode scaling up to 45 GPUs (3 nodes) and benchmark against hand-coded TeraChem integral code. Finally, we also outline our metaprogrammed Regent implementation, which enables flexible code generation for integrals of different angular momenta.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

NEAMS Reactor Physics Project Management and Coordination Activities

The following report summarizes the coordination activities and collaboration efforts by research staff at Oak Ridge National Laboratory, Idaho National Laboratory, and Argonne National Laboratory for the development of Shift and Griffin computer codes under the US Department of Energy’s Nuclear Energy Advanced Modeling and Simulation program.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2013

SCALE Uncertainty Quantification Methodology for Criticality Safety Analysis of Used Nuclear Fuel

A methodology based on stochastic sampling of input data covariances has been developed for uncertainty quantification with the SCALE code system. This provides the capability to determine uncertainties for a wide range of responses computed with any SCALE sequence. The methods used in the stochastic computation are discussed here for determining the uncertainty in the multiplication factor of used nuclear fuel (UNF), taking into account the impact of nuclear data uncertainties on the depletion calculations.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2015

Shields - Code Coupling

This PowerPoint presentation focuses on the history and benefits of the Space Weather Modeling Framework (SWMF) code and collaborative software development.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2016

Delivering Science on Day One

While benchmarking software is useful for testing the performance limits and stability of Argonne National Laboratory’s new Theta supercomputer, there is no substitute for running real applications to explore the system’s potential. The Argonne Leadership Computing Facility’s Theta Early Science Program, modeled after its highly successful code migration program for the Mira supercomputer, has one primary aim: to deliver science on day one. Here is a closer look at the type of science problems that will be getting early access to Theta, a next-generation machine being rolled out this year.

Williams, Timothy J.↗

DOE OSTI2019

BCL: A Cross-Platform Distributed Data Structures Library

One-sided communication is a useful paradigm for irregular parallel applications, but most one-sided programming environments, including MPI's one-sided interface and PGAS programming languages, lack application-level libraries to support these applications. We present the Berkeley Container Library, a set of generic, cross-platform, high-performance data structures for irregular applications, including queues, hash tables, Bloom filters and more. BCL is written in C++ using an internal DSL called the BCL Core that provides one-sided communication primitives such as remote get and remote put operations. The BCL Core has backends for MPI, OpenSHMEM, GASNet-EX, and UPC++, allowing BCL data structures to be used natively in programs written using any of these programming environments. Along with our internal DSL, we present the BCL ObjectContainer abstraction, which allows BCL data structures to transparently serialize complex data types while maintaining efficiency for primitive types. We also introduce the set of BCL data structures and evaluate their performance across a number of high-performance computing systems, demonstrating that BCL programs are competitive with hand-optimized code, even while hiding many of the underlying details of message aggregation, serialization, and synchronization.

Brock, Benjamin↗

DOE OSTI2022

Profiling and Optimization [Slides]

Intended for Simulating Physics using Efficient and Effective code Development (SPEED) program. This is a LANL internal lecture series for computational science application developers.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2022

Development of Integrated Thermal Fluids Modeling Capability for MSRs

The DOE Nuclear Energy Advanced Modeling and Simulation (NEAMS) program supports a full range of computational thermal fluids analysis capabilities and code developments for a broad class of light-water and advanced reactor concepts. The research and development approach under thermal fluids technical area synergistically combines three length and time scales in a hierarchal multi-scale approach. To demonstrate the feasibility and capabilities of a multi-scale thermal fluids capability using these codes, a key joint effort has been pursued to develop an integrated system-and engineering-scale thermal fluids analysis capability with the MOOSE-based codes, through integration of SAM and Pronghorn, both based on the MOOSE framework. This report summarizes the progress in developing an integrated system- and engineering-scale thermal fluids analysis capability based on SAM and Pronghorn for molten salt reactors (MSRs), which gained significant interest in recently years. Two coupling approaches were studied, i.e. separate domain or domain-segregated coupling approach and the domain-overlapping approach. A series of coupled multi-physics models have been developed for a common reference molten salt fast reactor (MSFR) concept, ranging from standalone SAM system model to integrated SAM-Pronghorn-Griffin models. Both the steady state and the transient simulations are performed to the state-of-the-art simulation capabilities of NEAMS software suite in MSFR system applications. This report also covers further development and testing of the gas transport model in SAM for MSR modeling support. The presence of noncondensable gas in MSR systems would have strong impacts on fission gas removal and transport of noble metals throughout the system. Fission products removed through the off-gas system can also impact reactivity and can act as an additional point of heat removal. To ensure that the gas transport model is adequately tested, the supported modeling capabilities and features of SAM were identified, and a suite of tests were developed to test the model for each identified feature. Validation and UQ testing were also performed for the model and demonstrated that the buoyancy term, which was originally developed using non-salt/helium gas experimental data, can capture the experimental gas bubble velocity and diameter to within experimental and code uncertainty. An existing MSRE model was also modified in this work to include the gas transport model and to demonstrate the gas model behavior for realistic conditions of interest.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2025

Integrated Molten Salt Reactor Modeling Capabilities in NEAMS Thermal Hydraulics Tools

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2016

Multiscale Modeling of Accident Tolerant Fuels under the NEAMS ATF Program

The U.S. Department of Energy's Nuclear Energy Advanced Modeling and Simulation (NEAMS) program has been developing computational analysis tools for nuclear fuel simulation. These codes include BISON and Marmot for investigation of fuel behavior at the continuum and microstructural scales, respectively. In 2014, NEAMS introduced what it calls High Impact Problems (HIPs) into its development plan. These HIPs are intended to make significant advancements in a particular area of nuclear power research in a short period of time (3 years or less). NEAMS has chosen an accident tolerant fuel (ATF) project, which emphasizes utilizing BISON and Marmot to model proposed materials, as its first HIP. Since the events that occurred at the Fukushima-Daiichi nuclear power plant in 2011, the U.S. Department of Energy's Office of Nuclear Energy accelerated research in nuclear fuel concepts with enhanced accident tolerance as part of its Fuel Cycle Research and Development (FCRD) Advanced Fuels Campaign (AFC). Accident tolerant fuels are expected to perform at least as well as conventional fuel during normal conditions and provide significantly increased response time in the event of an accident. Given the many unknowns associated with proposed ATF concepts, the research and development being undertaken by AFC in this area is a challenge, particularly considering the desire to have a lead test rod or assembly in a commercial plant by 2022. With the AFC as its primary stakeholder, the NEAMS ATF HIP is developing material models (using a multi-scale approach) for multiple candidate materials. Through a variety of analyses employing these models, the ATF HIP is providing insight and support to the AFC as it strives to understand these materials and prioritize further development. Use of computational tools such as BISON and Marmot are a vital component of the AFC's strategy since experimental data will not be available broadly and quickly enough to understand the proposed materials fully by the time the AFC must make further development decisions. This summary reviews the overall approach of the NEAMS ATF HIP. First, we give an overview of the current materials chosen for investigation. We also review the overall multi-scale approach to model development. We briefly review the work underway at multiple national laboratories to develop mechanistic engineering scale models based on lower length scale insight. Note that coordinated work is also underway at multiple universities, but those efforts are not detailed here. The NEAMS ATF HIP is assisting the AFC in assessing two accident tolerant materials, uranium silicide fuel and FeCrAl cladding. A multi-scale material model development approach is being undertaken to formulate the models necessary to investigate the materials over a range of normal and off-normal scenarios. This approach includes molecular dynamics, density functional theory, mesoscale modeling, and engineering scale modeling. Sensitivity studies are underway to understand the most critical scenarios and material model input parameters. The information generated is being given to the AFC for their use in selecting promising ATF concepts. (authors)

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2025

Integrated Molten Salt Reactor Modeling Capabilities in NEAMS Thermal Hydraulics Tools

The DOE neams program supports a full range of computational thermal fluids analysis capabilities and code developments for a broad range of advanced reactor concepts. The research and development approach under the thermal fluids technical area synergistically combines three length and time scales in a hierarchical multi-scale approach. To enable multi-scale thermal fluids capability using these codes, a key joint effort has been underway to develop an integrated system- and engineering-scale thermal fluids analysis capability, through integration of SAM and Pronghorn codes, both based on the MOOSE framework. This report summarizes recent advances in developing an integrated system- and engineering-scale modeling capability for the msr concept, which has gained significant interest in recent years. A consistent framework was established by coupling Pronghorn and SAM through the Saline interface, with thermophysical properties provided by the Molten Salt Thermal Property Database (MSTDB-TP). Further improvements were made to the coupling schemes and domain-overlapping strategies, enhancing the stability and robustness of multi-code simulations. Verification and validation efforts demonstrate the accuracy of this integration across a range of benchmark problems, including one-dimensional heated pipe flows, three-dimensional natural convection loops with evolving isotopic compositions, and \gls{msre} demonstration cases. Within Pronghorn, new capabilities were introduced to model corrosion and noble-metal plating phenomena, supported by an extended thermal-hydraulics framework and refined turbulence treatments. To capture two-phase flow behavior, a multiphase Euler–Euler model was implemented in Pronghorn, including advanced closure relations, high-resolution advection techniques, and capillary force reconstruction. Preliminary verification cases confirm the fidelity of the approach, while planned validation efforts target canonical multiphase benchmarks and application to msr components such as the msre pump bowl. Finally, updates to SAM’s msr mass transfer modeling were extended to consider noble gas migration into porous structures like graphite. The point kinetics model was updated to include reactivity feedback contributions from any defined species, such as xenon. The gas transport model was expanded for applicability to gas mixtures, bubble efflux phenomena, and species transport between liquid and gas phases. A selection of multi-scale Sherwood number correlations from MOSCATO/NekRS and multi-phase correlations from literature have been added for improved accuracy in calculating mass transfer coefficients. A companion effort on developing system-level redox corrosion has also been incorporated into SAM. Collectively, these enhancements strengthen the predictive capability of SAM and Pronghorn for simulating MSR thermal-hydraulics, corrosion, multiphase behavior, and fission-product transport, providing a more complete toolset for design, safety analysis, and licensing support of next-generation \gls{msr}s.

42 - ENGINEERING↗

DOE OSTI2022

WORM (Write One, Read Many)

WORM (Write One, Run Many) is an easy to use, cross platform, embedded and extensible, functional programming language designed to facilitate the creation of input-decks for computer codes that use standard ASCII text files for input. WORM makes it easy to create generic (yet, complex and powerful) reusable models. Additionally its nature allows for complex calculations and routines to be coded once and easily reused, further simplifying the creation of input decks. WORM (Write One, Run Many) is a powerful and versatile tool designed to improve the efficiency of today’s criticality safety analyst by allowing: + input decks for parametric studies to be created quickly and easily, + calculations and variables to be imbedded into any input deck, thus allowing for meaningful parameter specifications, + problems to be specified using any combination of units, and + complex mathematically defined models to be created. A very simple syntax is employed, and therefore the WORM is easy to learn. A WORM model is essentially a standard input deck with some of its numerical values replaced by WORM code. WORM code may include and evaluate the following mathematical operators and functions: addition, subtraction, multiplication, division, exponentiation, modulus, sine, cosine, tangent, arcsine, arccosine, arctangent, the natural logarithm, logarithm base 10, integer truncation, absolute value, and random number. Several common constants, e.g., pi, e, and Avogadros’s Number (both as 6.022e23 and 0.6022), are predefined in WORM. Additionally, many unit conversion factors are also predefined: millimeters, meters, inches, feet, yards, and mils to centimeters; kilograms, pounds, and ounces to grams; liters, milliliters, gallons, and fluid ounces to cubic centimeters; and angular degrees to radians. For parametric studies, WORM supports various shorthand list specifications: the explicit step size, linear interpolation, and logarithmic interpolation. The list notation sequentially assigns multiple values to a name. WORM creates an input deck for each value of the name. If multiple lists are used, WORM steps through each list individually, i.e., WORM creates input decks corresponding to each and every permutation of the list values. Additionally, a library of standard material definitions and Perl subroutines are included. Any one of these files can be incorporated into the subject model with a simple WORM read command. WORM is completely written in Perl, the Practical Extraction and Reporting Language. Perl is one of the most portable programming languages available today. As such, the WORM works on practically any computer platform.

Sartor, Raymond↗

DOE OSTI2015

Exploring Asynchronous Many-Task Runtime Systems toward Extreme Scales

Major exascale computing reports indicate a number of software challenges to meet the dramatic change of system architectures in near future. While several-orders-of-magnitude increase in parallelism is the most commonly cited of those, hurdles also include performance heterogeneity of compute nodes across the system, increased imbalance between computational capacity and I/O capabilities, frequent system interrupts, and complex hardware architectures. Asynchronous task-parallel programming models show a great promise in addressing these issues, but are not yet fully understood nor developed su ciently for computational science and engineering application codes. We address these knowledge gaps through quantitative and qualitative exploration of leading candidate solutions in the context of engineering applications at Sandia. In this poster, we evaluate MiniAero code ported to three leading candidate programming models (Charm++, Legion and UINTAH) to examine the feasibility of these models that permits insertion of new programming model elements into an existing code base.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2021

Radiation Hydrodynamics in the Lagrangian Application Project’s LUMOS code

Starting in 2019, the Lagrangian Applications Project (LAP) and the Transport Project set out to develop a new ALE/Lagrangian radiation-hydrodynamics (RH) capability in a new code product named LUMOS. This work was done under the guidance of the Advanced Simulation and Computing (ASC) program with the goal of producing software capable of leveraging the high-order thermal radiative transfer (TRT) solvers provided by the Jayenne and Capsaicin software projects. This capability supplements the existing gray diffusion solver that is currently available in LAP’s FLAG code [1, 2, 3] for RH. The remainder of this memo describes the coupling of the radiation and hydrodynamics solvers within LAP’s LUMOS code. Initially delivered in 2020 as part of an L2 milestone [4], this capability continues to mature in FY21 with more efficient and robust algorithms, new support for ALE, and support for mixed materials per cell. Today, LUMOS is provided as a standard end-user product in the suite of LAP tools provided in each release cycle. Code access can be requested at https://asc.lanl.gov.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2020

CSRI Summer Proceedings 2020

The Computer Science Research Institute (CSRI) brings university faculty and students to Sandia for focused collaborative research on Department of Energy (DOE) computer and computational science problems. The institute provides an opportunity for university researchers to learn about problems in computer and computational science at DOE laboratories. Participants conduct leading-edge research, interact with scientists and engineers at the laboratories, and help transfer results of their research to programs at the labs. Some specific CSRI research interest areas are: scalable solvers, optimization, adaptivity and mesh refinement, graph-based, discrete, and combinatorial algorithms, uncertainty estimation, mesh generation, dynamic load-balancing, virus and other malicious-code defense, visualization, scalable cluster computers, data-intensive computing, environments for scalable computing, parallel input/output, advanced architectures, and theoretical computer science. The CSRI Summer Program is organized by CSRI and typically includes the organization of a weekly seminar series and the publication of a summer proceedings. In 2020, the CSRI summer program was executed completely virtually; all student interns worked from home, due to the COVID-19 pandemic.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2017

Verification of EPA's " Preliminary remediation goals for radionuclides" (PRG) electronic calculator

The U.S. Environmental Protection Agency (EPA) requested an external, independent verification study of their “Preliminary Remediation Goals for Radionuclides” (PRG) electronic calculator. The calculator provides information on establishing PRGs for radionuclides at Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) sites with radioactive contamination (Verification Study Charge, Background). These risk-based PRGs set concentration limits using carcinogenic toxicity values under specific exposure conditions (PRG User’s Guide, Section 1). The purpose of this verification study is to ascertain that the computer codes has no inherit numerical problems with obtaining solutions as well as to ensure that the equations are programmed correctly.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2014

Final Project Report "Advanced Concept Exploration For Fast Ignition Science Program"

The Fast Ignition (FI) Concept for Inertial Confinement Fusion has the potential to provide a significant advance in the technical attractiveness of Inertial Fusion Energy (IFE) reactors. FI differs from conventional “central hot spot” (CHS) target ignition by decoupling compression from heating: using the laser (or heavy ion beam or Z pinch) drive pulse (10’s of ns) to create a dense fuel and a second, much shorter (~10 ps) high intensity pulse to ignite a small region of it. There are two major physics issues concerning this concept; controlling the laser-induced generation of large electron currents and their propagation through high density plasmas. This project has addressed these two significant scientific issues in Relativistic High Energy Density (RHED) physics. Learning to control relativistic laser matter interaction (and the limits and potential thereof) will enable a wide range of applications. While these physics issues are of specific interest to inertial fusion energy science, they are also important for a wide range of other HED phenomena, including high energy ion beam generation, isochoric heating of materials, and the development of high brightness x-ray sources. Generating, controlling, and understanding the extreme conditions needed to advance this science has proved to be challenging: Our studies have pushed the boundaries of physics understanding and are at the very limits of experimental, diagnostic, and simulation capabilities in high energy density laboratory physics (HEDLP). Our research strategy has been based on pursuing the fundamental physics underlying the Fast Ignition (FI) concept. We have performed comprehensive study of electron generation and transport in fast-ignition targets with experiments, theory, and numerical modeling. A major issue is that the electrons produced in these experiments cannot be measured directly—only effects due to their transport. We focused mainly on x-ray continuum photons from bremsstrahlung and x-ray line radiation from K-shell fluorescence. Integrated experiments, which combine target compression with short-pulse laser heating, yield additional information on target heating efficiency. This indirect way of studying the underlying behavior of the electrons must be validated with computational modeling to understand the physics and improve the design. This program execution required a large, well-organized team and it was managed by a joint Collaboration between General Atomics (GA), Lawrence Livermore National Laboratory (LLNL), and the Laboratory for Laser Energetics (LLE). The Collaboration was formed 8 years ago to understand the physics issues of the Fast Ignition concept, building on the strengths of each partner. GA fulfills its responsibilities jointly with the University of California, San Diego (UCSD), The Ohio State University (OSU) and the University of Nevada at Reno (UNR). Since RHED physics is pursued vigorously in many countries, international researchers have been an important part of our efforts to make progress. The division of responsibility was as follows: (1) LLE had primary leadership for channeling studies and the integrated energy transfer, (2) LLNL led the development of measurement methods, analysis, and deployment of diagnostics, and (3) GA together with UCSD, OSU and UNR studied the detailed energy-transfer physics. The experimental program was carried out using the Titan laser at the Jupiter Laser Facility at LLNL, the OMEGA and OMEGA EP lasers at LLE and the Texas Petawatt laser (TPW) at UT Austin. Modeling has been pursued on large computing facilities at LLNL, OSU, and UCSD using codes developed (by us and others) within the HEDLP program, commercial codes, and by leveraging existing supercomputer codes developed by the NNSA ICF program. This Consortium brought together all the components—resources, facilities, and personnel—necessary to accomplish its aggressive goals. The ACE Program has been strongly collaborative, taking advantage of the expertise of the participating institutions to provide a research effort that is far greater than the sum of its parts. The results of this work have firmly strengthened the scientific foundation from which the viability of FI and other applications can be evaluated. Program execution has also led to improved diagnostics for probing dense, hot plasmas, detailed understanding of high-current, relativistic electron energy generation and transport across boundaries and into dense plasmas, and greatly enhanced predictive modeling capabilities. One important aspect of this program was the involvement and training of young scientists including postdoctoral fellows and graduate students. During the entire 8 years of FI and ACE project period since 2005, more than fifteen graduate students completed their doctoral dissertations including three from OSU and two from UCSD in last three years. This project generated an impressive forty articles in high quality journals including nine (including two under review) in Physical Review Letters during the last funding period since 2011.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗