On policy iteration as a Newton's method and polynomial policy iteration algorithms
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Bibliographic record
Abstract
Policy iteration is a popular technique for solving Markov decision processes (MDPs). It is easy to describe and implement, and has excellent performance in practice. But not much is known about its complexity. The best upper bound remains exponential, and the best lower bound is a trivial Ω(n) on the number of iterations, where n is the number of states. This paper improves the upper bounds to a polynomial for policy iteration on MDP problems with special graph structure. Our analysis is based on the connection between policy iteration and Newton’s method for finding the zero of a convex function. The analysis offers an explanation as to why policy iteration is fast. It also leads to polynomial bounds on several variants of policy iteration for MDPs for which the linear programming formulation requires at most two variables per inequality (MDP(2)). The MDP(2) class includes deterministic MDPs under discounted and average reward criteria. The bounds on the run times include O(mn 2 log m log W) on MDP(2) and O(mn 2 log m) for deterministic MDPs, where m denotes the number of actions and W denotes the magnitude of the largest number in the problem description. 1
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| 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 it