PRISM¶

PRISM (Precision-aware Reduction In-Switch Module) is an open-source RTL research prototype for “in-network collective” (INC) operations on FPGA-based packet-processing datapaths. The project studies how reduction-oriented collective operations, such as REDUCE_SUM¹ aggregation, can be partially offloaded from the host accelerator (CPU/GPU) communication stack into the network data plane itself. In this sense, PRISM is inspired by the same broad direction as Mellanox/NVIDIA SHARP², which demonstrated that collective reduction processing can be moved into network switching hardware to reduce communication overhead and improve collective latency.

The datapath exposes a 512-bit AXI-Stream interface. OpenNIC is the reference platform for the first prototype: it provides the FPGA shell in which PRISM is synthesized and the integration with the NIC, host drivers, and software.

From a numerical perspective, PRISM focuses on reproducible floating-point reductions. Conventional FP32 reductions are sensitive to operand ordering because floating-point addition is not associative; different reduction trees or scheduling orders may produce different bit-level results. PRISM therefore compares the baseline FP32_ARRIVAL profile against a Kulisch-style³ long-accumulator approach, with the goal of studying the area, latency, throughput, and reproducibility trade-offs of exact or near-exact accumulation in a streaming network datapath.

The target architecture is a reusable, port-parameterized collective core. It implements buffering, backpressure, CONTROL, reduction, result routing, and replication; OpenNIC profiles adapt the same RTL to one U50 CMAC or two U280 CMACs. Forwarding, VOQs, a general crossbar, and multi-switch aggregation remain later integration work.

The latest source code is available from the PRISM GitHub repository.

Citation¶

If you use PRISM in your project, please cite the repository and/or the thesis:

@misc{prism-repository,
  author = {Cipolletti, Lorenzo},
  title = {PRISM Repository},
  year = {2026},
  howpublished = {\url{https://github.com/uniquadev/prism}},
  note = {Bachelor thesis project repository}
}

@mastersthesis{cipolletti-prism-thesis,
  author = {Cipolletti, Lorenzo},
  title = {Development of Primitive Hardware for Network Computing},
  school = {Sapienza University of Rome},
  year = {2026},
  type = {Bachelor thesis},
  note = {Supervisor: Salvatore Pontarelli; co-supervisor: Daniele De Sensi}
}

Reading guide¶