Programmer-Centric Conditions for Itanium Memory Consistency
Bibliographic record
Abstract
A programmer-centric model of memory consistency provides a sequence of instructions for each proces- sor, and requires that these sequences satisfy a collection of rules. It also requires that the notion of validity of a sequence is the natural one: the value read from a shared memory location must be one that was written by the most recent preceding instruction that stored to the same location. A programmer-centric model supports reasoning about programs at a non-operational level. It is not obscured by the implementation details of the underlying architecture. In this paper, we formulate a programmer-centric description of the memory consistency model provided by the Itanium architec- ture. However, our definition is not tight. We provide two very similar definitions, each motivated by slightly different implementations of load-acquire instructions, and prove that the specification of the Itanium memory model lies strictly between the two. We also entertain a handful of other natural notions of load-acquire rules and show that none exactly captures the Itanium specification. This leads us to question whether the specification of the Itanium memory order [5] is actually faithful to the Itanium architects' intentions.
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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 | 0.010 | 0.032 |
| Meta-epidemiology (narrow) | 0.001 | 0.002 |
| Meta-epidemiology (broad) | 0.002 | 0.002 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.003 | 0.009 |
| Scholarly communication | 0.007 | 0.015 |
| Open science | 0.004 | 0.006 |
| Research integrity | 0.005 | 0.008 |
| Insufficient payload (model declined to judge) | 0.007 | 0.002 |
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".