HPSF Conference 2025

1. A Brief Overview of LANL's use of Kokkos - Daniel Holladay, Los Alamos National Laboratory (20 minutes)
Since the commissioning of the first petascale machine, Roadrunner, in 2009 at the Los Alamos
National Laboratory (LANL), the ability for physics codes at LANL to take advantage of accelerators
has provided utility and productivity improvements for code users. The ability to take advantage of an
accelerator, and more specifically general purpose graphics processing units (GPGPUs), will quickly
move from a productivity enhancement to absolutely necessary as more than 90% of the compute
capability of the El Capitan supercomputer at Lawrence Livermore National Laboratory (LLNL) will
only be accessed through effective use of its GPGPUs, a task which has traditionally been
accomplished with vendor specific software extensions such as CUDA or HIP. Many projects with
code bases ranging from large and established FORTRAN codes to new c++ based projects have
made the decision to use Kokkos as the tool that will enable effective use of LLNL's El Capitan
compute resources as well as future machines which could likely benefit from Kokkos's capabilities.
In this talk I will give an overview of several physics code projects at LANL and their usage of Kokkos.

2. Enhancing Fortran Code for Operational Weather Forecasting with Kokkos: Results and Lessons Learned - Timothy Sliwinski, Cooperative Institute for Research in the Atmosphere (CIRA) (20 minutes)
At NOAA, much of the code for numerical weather prediction (NWP) and operational weather forecasting is built upon Fortran, into which decades of scientific research knowledge and expertise has been invested. Therefore, moving away from Fortran and potentially breaking what has been a highly reliable system for many years is a significant challenge.
To demonstrate new methods to modernize NOAA’s NWP models, Kokkos was selected due to its ability to work across multiple GPUs and CPUs with a single source code and the presence of the Fortran Language Compatibility Layer (FLCL), easing development of the interface between Fortran and C++ Kokkos kernels. As a first step, the YSU Planetary Boundary Layer (PBL) scheme was chosen as the target and a prototype with Kokkos was developed, tested, and performance benchmarked. In this presentation, we report the performance of this new Kokkos-enhanced Fortran code on CPU and an Nvidia GPU, the challenges of the C/Fortran interface, potential future prospects for the use of Kokkos at NOAA, and overall lessons learned from this project for anyone else interested in using Kokkos with existing Fortran source codes.

3. Using Umpire's Memory Management Capabilities with Kokkos - Kristi Belcher, LLNL (20 minutes)
Umpire is an open-source data and memory management library created at Lawrence Livermore National Laboratory (LLNL). Although Umpire is part of the RAJA Portability Suite, it was made to be modular and can therefore be used with Kokkos and other performance portability abstractions. Umpire provides memory pools which avoid expensive calls to the underlying device-specific API making allocations, large or small, performant in HPC environments. Umpire provides numerous types of memory resources and allocators (i.e. Device, Host, Unified Memory, IPC Shared Memory, etc.). In this talk, I will discuss key Umpire features and capabilities and showcase a Kokkos example with Umpire.

4. Early Experiences Using Kokkos for Multi-Resolution Analysis - Joseph Schuchart, Stony Brook University (20 minutes)
MADNESS is a framework for multi-resolution analysis with application in quantum chemistry. In this talk, we will present some early experiences in using Kokkos in a port of MADNESS to the TTG data-flow programming model, which includes both a restructuring of the existing program flow and a port to accelerators.