Better Together: Combining Analytical and Annealing Methods for FPGA Placement
Bibliographic record
Abstract
Placement is a critical step in the FPGA design implementation flow that strongly impacts routability and timing closure. Recent state-of-the-art academic analytical placers have achieved impressive scalability but are limited to AMD Ultrascale-like architectures and mostly synthetic designs. On the other hand, VPR, the place and route tool within the widely used open-source Verilog-to-Routing (VTR) toolchain, can produce a legal placement for any arbitrary architecture; however, its simulated annealing placer scales poorly. Thus, there is a clear need to bring scalable, high-quality placement to realistic architectures and circuits. In this work, we develop a hybrid framework that combines the strength of a scalable flat analytical placer with the flexibility of simulated annealing techniques to adapt to various architectures and circuits, substantially improving the quality of results. We augment the state-of-theart analytical elfPlace FPGA placer as aug-elfPlace, generalizing its architecture modeling to handle real-world constraints and target different and more complete architectures. We leverage VPR’s legalization capability to integrate with external placers such as aug-elfPlace. VPR’s simulated annealing placer can further optimize the legalized placement, and VPR’s router and timing analysis can provide final quality results. By integrating wirelength-driven aug-elfPlace and VPR, our hybrid framework achieves up to 2% timing improvement with 15% reduction in routed wirelength compared to timing-driven VPR, on average across the large and heterogeneous Titan23 benchmark suite targeting an Intel Stratix-IV-like architecture.
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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 | 0.001 | 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 | 0.000 | 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".