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Daniel Waters

Daniel Waters
Daniel Waters
Computer Systems Engineer

Daniel Waters is a Computer Systems Engineer in CLaSS and also works with CRD’s Applied Numerical Analysis Group on Proto.

His current research focus is on implementing an efficient stencil-calculation algorithm using CUDA.

Originally from Groton, MA, he earned his B.A. degree from Kenyon College in 2014 and his master’s from the University of Chicago in 2016. His interest in HPC and working at national labs (he’s worked at three now: Argonne, Livermore, and Berkeley) was initially sparked during his tenure at the University of Chicago.

Conference Papers

Daniel Waters, Colin A. MacLean, Dan Bonachea, Paul H. Hargrove, "Demonstrating UPC++/Kokkos Interoperability in a Heat Conduction Simulation (Extended Abstract)", Parallel Applications Workshop, Alternatives To MPI+X (PAW-ATM), November 2021, doi: 10.25344/S4630V

We describe the replacement of MPI with UPC++ in an existing Kokkos code that simulates heat conduction within a rectangular 3D object, as well as an analysis of the new code’s performance on CUDA accelerators. The key challenges were packing the halos in Kokkos data structures in a way that allowed for UPC++ remote memory access, and streamlining synchronization costs. Additional UPC++ abstractions used included global pointers, distributed objects, remote procedure calls, and futures. We also make use of the device allocator concept to facilitate data management in memory with unique properties, such as GPUs. Our results demonstrate that despite the algorithm’s good semantic match to message passing abstractions, straightforward modifications to use UPC++ communication deliver vastly improved performance and scalability in the common case. We find the one-sided UPC++ version written in a natural way exhibits good performance, whereas the message-passing version written in a straightforward way exhibits performance anomalies. We argue this represents a productivity benefit for one-sided communication models.


Paul H. Hargrove, Dan Bonachea, Max Grossman, Amir Kamil, Colin A. MacLean, Daniel Waters, "UPC++ and GASNet: PGAS Support for Exascale Apps and Runtimes", Poster at Exascale Computing Project (ECP) Annual Meeting 2021, April 2021,

We present UPC++ and GASNet-EX, which together enable one-sided, lightweight communication such as arises in irregular applications, libraries and frameworks running on exascale systems.

UPC++ is a C++ PGAS library, featuring APIs for Remote Memory Access (RMA) and Remote Procedure Call (RPC).  The combination of these two features yields performant, scalable solutions to problems of interest within ECP.

GASNet-EX is PGAS communication middleware, providing the foundation for UPC++ and Legion, plus numerous non-ECP clients.  GASNet-EX RMA interfaces match or exceed the performance of MPI-RMA across a variety of pre-exascale systems

Amir Kamil, John Bachan, Dan Bonachea, Paul H. Hargrove, Erich Strohmaier and Daniel Waters, "UPC++: Asynchronous RMA and RPC Communication for Exascale Applications", Poster at Exascale Computing Project (ECP) Annual Meeting 2020, February 2020,