Learn the Switches: Evolving FPGA NoCs with Stall-Free and Backpressure Based Routers
Bibliographic record
Abstract
We can overcome the pessimism in worst-case routing latency analysis of timing-predictable Network-on-Chip (NoC) workloads by single digit factors through the use of a hybrid FPGA-optimized NoC. Timing-predictable FPGA-optimized NoCs such as HopliteBuf integrate stall-free FIFOs that are sized using offline, static analysis of a user-supplied flow pattern and rates. For certain bursty traffic and flow configurations, the static analysis delivers very large, sometimes infeasible, FIFO size bounds and large worst-case latency bounds. Alternatively, backpressure-based NoCs such as HopliteBP can operate with lower latencies for certain bursty flows. However, they suffer from severe pessimism in the analysis due to the effect of pipelining of packets and interleaving of flows at switch ports. As we show in this paper, a hybrid FPGA NoC that seamlessly composes both design styles on a per-switch basis, delivers the best of both worlds with improved feasibility (bounded operation), and tighter latency bounds. We select the NoC switch configuration though a novel evolutionary algorithm based on Maximum Likelihood Estimation (MLE). For synthetic (RANDOM, LOCAL) and real world (SpMV, Graph) workloads, we demonstrate ≈2– 3× improvements in feasibility, ≈1–6.8× in worst-case latency while only requiring LUT cost ≈1–1.5× larger than the cheapest HopliteBuf solution. We also deploy and verify our NoC (PL) and MLE framework (PS) on a Pynq-Z1 to adapt and reconfigure NoC switches dynamically.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".