PopuLoRA: Co-Evolving LLM Populations for Reasoning Self-Play

Fuente: arXiv
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Main Authors: Castanyer, Roger Creus, Bradway, Geoffrey, Wolf, Lorenz, Lin, Maxwill, Mavor-Parker, Augustine N., Sargent, Matthew James
Format: Preprint
Published: 2026
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author Castanyer, Roger Creus
Bradway, Geoffrey
Wolf, Lorenz
Lin, Maxwill
Mavor-Parker, Augustine N.
Sargent, Matthew James
author_facet Castanyer, Roger Creus
Bradway, Geoffrey
Wolf, Lorenz
Lin, Maxwill
Mavor-Parker, Augustine N.
Sargent, Matthew James
contents We introduce PopuLoRA, a population-based asymmetric self-play framework for reinforcement learning with verifiable rewards (RLVR) post-training of LLMs. Teachers and students are specialised LoRA adapters on a shared frozen base: teachers propose problems, matched students solve them under a programmatic verifier, and cross-evaluation between sub-populations replaces the self-calibration that limits single-agent self-play. A family of LoRA weight-space evolution operators (mutations and crossovers that produce same-rank population members in seconds) serves as the replacement step of a population-based training loop at 7B scale. We instantiate PopuLoRA on top of Absolute Zero Reasoner and compare it against a per-adapter compute-matched single-agent baseline. Where the single agent self-calibrates to generating easy problems it can reliably solve, the population enters a co-evolutionary arms race: teachers produce increasingly complex problems, student solve rates oscillate, and problem-space coverage keeps expanding throughout training. Despite lower training-time reward, the population mean outperforms the baseline on three code benchmarks (HumanEval+, MBPP+, LiveCodeBench) and seven math benchmarks (AIME 24/25, AMC 23, MATH-500, Minerva, GSM8K, OlympiadBench), and even the weakest member of the population beats the baseline on aggregate.
format Preprint
id arxiv_https___arxiv_org_abs_2605_16727
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle PopuLoRA: Co-Evolving LLM Populations for Reasoning Self-Play
Castanyer, Roger Creus
Bradway, Geoffrey
Wolf, Lorenz
Lin, Maxwill
Mavor-Parker, Augustine N.
Sargent, Matthew James
Artificial Intelligence
We introduce PopuLoRA, a population-based asymmetric self-play framework for reinforcement learning with verifiable rewards (RLVR) post-training of LLMs. Teachers and students are specialised LoRA adapters on a shared frozen base: teachers propose problems, matched students solve them under a programmatic verifier, and cross-evaluation between sub-populations replaces the self-calibration that limits single-agent self-play. A family of LoRA weight-space evolution operators (mutations and crossovers that produce same-rank population members in seconds) serves as the replacement step of a population-based training loop at 7B scale. We instantiate PopuLoRA on top of Absolute Zero Reasoner and compare it against a per-adapter compute-matched single-agent baseline. Where the single agent self-calibrates to generating easy problems it can reliably solve, the population enters a co-evolutionary arms race: teachers produce increasingly complex problems, student solve rates oscillate, and problem-space coverage keeps expanding throughout training. Despite lower training-time reward, the population mean outperforms the baseline on three code benchmarks (HumanEval+, MBPP+, LiveCodeBench) and seven math benchmarks (AIME 24/25, AMC 23, MATH-500, Minerva, GSM8K, OlympiadBench), and even the weakest member of the population beats the baseline on aggregate.
title PopuLoRA: Co-Evolving LLM Populations for Reasoning Self-Play
topic Artificial Intelligence
url https://arxiv.org/abs/2605.16727