Guiding Inferences in Connection Tableau by Recurrent Neural Networks
Paper · 2019 · Bartosz Piotrowski and Josef Urban
Summary
Connection-style theorem provers such as leanCoP must repeatedly decide which input clause to use when extending an open branch of the proof tree. Poor choices lead to wasted search and backtracking. The authors treat this decision as a sequence-to-sequence problem. They extracted 13,822 connection proofs of Mizar Mathematical Library (MML) problems, translated to TPTP. From these proofs they built training pairs that map either the literals or the clauses along a branch to the clause that was actually used next. Variables and Skolem functions were normalized to the tokens VAR and SKLM. A neural machine translation model (Luong et al.) encodes the branch into a hidden state and decodes one or more clause choices. The literal-based input performed best, and accuracy increased with branch length. The model clearly outperformed a feature-based XGBoost baseline on longer paths. A further experiment had the model generate the next literal symbol by symbol, which ranking methods cannot do. The results suggest that encoding the evolving proof state with recurrent networks is a promising basis for internal prover guidance.
Key points
- The dataset contains 567,273 (path, next clause) pairs for each input type, plus variants that predict 2–3 consecutive clauses. Proofs were split 0.6/0.1/0.3 for train/validation/test, and the data is released on GitHub (BartoszPiotrowski/guiding-connection-tableau-by-RNNs).
- Predicting the next clause from literal paths reached 0.64 accuracy (top-1) and 0.72 (top-10). Clause paths gave only 0.17 and 0.36. Predicting two or three steps ahead was much weaker, at 0.11 and 0.05 top-1.
- NMT accuracy grew with input length and reached 0.85 for paths of length 8.
- The XGBoost multilabel baseline was trained on the MPTP2078 subset, which has 1383 clause labels. It averaged 0.43 and never exceeded 0.51. It did better than NMT only on very short paths.
- Conjecturing literals from 6442 available symbols achieved 0.08 accuracy overall and up to 0.34 on longer inputs. Long literals were often wrong or syntactically malformed.
Institutions
Fields, topics and concepts
📚 Shelves 2The field of science this work belongs to (OpenAlex fields).Computer Science · 19,503 worksArtificial Intelligence · 18,805 works
🧭 Topics 1Research subjects and languages the work is about.Reasoning · 1,948 works
Cite
Cite as Bartosz Piotrowski and Josef Urban. 2019. Guiding Inferences in Connection Tableau by Recurrent Neural Networks. arXiv:1905.07961.
@misc{piotrowski2019guiding,
title = {{Guiding Inferences in Connection Tableau by Recurrent Neural Networks}},
author = {Bartosz Piotrowski and Josef Urban},
year = {2019},
doi = {10.48550/arxiv.1905.07961},
eprint = {1905.07961},
archivePrefix = {arXiv},
url = {https://doi.org/10.48550/arxiv.1905.07961}
}References
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