The QCDOC supercomputer: hardware, software, and performance
Bibliographic record
Abstract
An overview is given of the QCDOC architecture, a massively parallel and highly scalable computer optimized for lattice QCD using system-on-a-chip technology. The heart of a single node is the PowerPC-based QCDOC ASIC, developed in collaboration with IBM Research, with a peak speed of 1 GFlop/s. The nodes communicate via high-speed serial links in a 6-dimensional mesh with nearest-neighbor connections. We find that highly optimized four-dimensional QCD code obtains over 50% efficiency in cycle accurate simulations of QCDOC, even for problems of fixed computational difficulty run on tens of thousands of nodes. We also provide an overview of the QCDOC operating system, which manages and runs QCDOC applications on partitions of variable dimensionality. Finally, the SciDAC activity for QCDOC and the message-passing interface QMP specified as a part of the SciDAC effort are discussed for QCDOC. We explain how to make optimal use of QMP routines on QCDOC in conjunction with existing C and C++ lattice QCD codes, including the publicly available MILC codes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.002 | 0.006 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.011 | 0.005 |
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 source (direct Gemma or distilled Codex), 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".