Calibration-Preserving Pruning: Compression as a Reliability Contract

arXiv:2608.23744 · cs.LG, cs.CL · Submitted 2026-08-24 · Read on arXiv

cs.LG, cs.CL

Submitted: 2026-08-24

Updated: 2026-08-24

License: http://creativecommons.org/licenses/by/4.0/

The gist: Split conformal prediction, not the pruning rule, supplies finite-sample marginal coverage once a pruned model is fixed independently of the conformal calibration split.

Terminology

Abstract

Split conformal prediction, not the pruning rule, supplies finite-sample marginal coverage once a pruned model is fixed independently of the conformal calibration split. We study the separate efficiency problem: can pruning preserve score geometry well enough to obtain smaller valid prediction sets? Calibration-Preserving Pruning (CPP) augments a base pruning score with nonconformity-gradient saliency and uses disjoint pruning, validation-selection, conformal-calibration, and test splits. Bounded score perturbations imply bounded conformal-quantile shifts and controlled set inflation, but do not make the generic coverage theorem CPP-specific. Final five-seed Qwen2.5-1.5B results at 50% sparsity show the largest gains on large-label tasks. On DBpedia-14, CPP-SparseGPT reduces mean set size from 10.1 to 8.6 while changing accuracy from 0.347 to 0.366; CPP-Wanda reduces 11.2 to 9.0 with an accuracy trade-off from 0.310 to 0.295. Across 15 dataset--sparsity cells, CPP-SparseGPT produces smaller sets in 13 and higher accuracy in 11. Matched controls show that generic supervised gradients explain much of the gain: true-label CPP is not statistically resolved from matched Wanda+SNIP, whereas threshold-aware candidate-label CPP reaches 7.8 mean set size at explicit accuracy and offline-compute costs. RoBERTa-base and Llama-3-8B diagnostics support transfer, but our claims remain limited to reliability-sensitive classification.

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