Your Benchmark Is an Empirical Measure Over Difficulty

What it claims

Across 25 popular benchmarks in 7 domains, the authors report that benchmarks fail in two different ways. Many benchmarks overweight certain difficulty regions, and the authors say their leaderboard conclusions "should be interpreted with caution." Others leave large parts of the difficulty axis without items, so they cannot track how a model improves during training. A benchmark can therefore rank finished models in a misleading way, or it can miss progress made during training. The two problems call for different fixes.

How it works

Each benchmark item gets an estimated difficulty, so the benchmark becomes an empirical distribution over difficulty. Measure mismatch compares that distribution with the intended one. A coverage gap is a stretch of the difficulty axis with no items, where gains made in training stay invisible. Each failure mode has its own diagnostic metric, and the authors say both come with theoretical guarantees.

BenchFill addresses coverage gaps. It rewrites existing items so they land at a chosen difficulty, which adds new examples in the under-represented regions of the benchmark. The authors call it "simple" and say it "effectively reduces local coverage gaps."

How to use it

The Hugging Face page lists one dataset that cites the paper. It lists no models, Spaces or collections. The paper text can be pulled with the Hugging Face CLI:

hf papers read 2610.29927

Limits

The page shows only the abstract and community comments. It does not name the 25 benchmarks or the 7 domains. It does not say which benchmarks show mismatch and which show coverage gaps. It does not explain how item difficulty is estimated, how the two metrics are defined, or what they score on any benchmark. It does not say which model BenchFill uses to rewrite items. It gives no figures for how much BenchFill shrinks the gaps, and it does not say how the rewritten items are checked for correctness. The page also does not name the citing dataset or say whether code or difficulty estimates are released.