geosearch-reranker

geosearch-reranker

CatboOst YetiRank listwise reranker, the last stage of a multilingual toponym search pipeline:

text
  -> GLiNER NER
  -> char-n-gram BM25 retrieval
  -> CatBoost reranker (this model)
  -> ranked GeoNames places

It reorders a fixed candidate set; it does not choose one. Retrieval ends by ranking on BM25 score with population as the tiebreak and cutting to top-k, and the model only permutes those survivors.

Results

Feature contract

The loader validates feature_names_ against this exact list and refuses a model that does not match, so a checkpoint trained on a different feature set degrades to retriever order instead of scoring garbage. Published so that failure is diagnosable by someone who did not train it:

1. city_entities
2. country_entities
3. admin1_entities
4. document
5. log_population
6. retriever_score
7. retriever_rank
8. city_exact_match
9. city_substr_match
10. city_ngram_containment
11. city_token_cover
12. country_match
13. has_country_span
14. admin1_substr_match
15. admin1_ngram_containment
16. has_admin1_span

Text features (CatBoost text_features) are the NER spans split by type — city_entities / country_entities / admin1_entities — plus the candidate document.

The typed split does not by itself match a span against a candidate. CatBoost builds a bag of words per text column independently, so it never sees the intersection of city_entities and document. A model trained on the split alone gave all three entity buckets 1.5% of its importance combined and scored below the retriever's own order. The overlap is therefore computed explicitly — the *_match / *_containment / *_cover features above — with has_country_span / has_admin1_span so a real mismatch (0.0) stays distinguishable from "no comparison was possible" (-1.0).

Document format

The document a candidate is scored against is three lines:

<name> | <name> | <name>
<country in English>
<admin1 region in English>

The ' | ' separator is load-bearing. Joined by a space instead, a place's spellings collapse into one pseudo-name whose n-grams are only ~1/n covered by a span naming it once — which turns the containment feature into an inverse-popularity signal. Separated, each spelling is matched alone and the best wins.

Training provenance

• use_gold_entities: False

That flag has to be false for a servable model. true trains on the query dataset's gold spans instead of mined NER output — a useful ablation ("how good would this be if NER were perfect?") that breaks train/serve parity by design, because online the reranker always receives GLiNER spans. A model trained with it set must not be served, and this line is on the card so that cannot happen silently.

• iterations: 1000
• learning rate: 0.05
• NDCG@k: 10
• trained at: 2026-09-09T17:00:55+00:00

Split by query, not by place: a query is the ranking group, so splitting on geonameid would tear one query's candidates across train and test — leaking the query and leaving positive-less test groups.

Known gap

admin1_name exists in English only (admin1CodesASCII.txt), so the admin1 features work for en/tr and read 0 for ru/zh. Regions are feature_class='A' and the ETL loads only 'P', so no localised region names were ever ingested.

Data licence and attribution

Derived from GeoNames, licensed CC BY 4.0.

Modifications made to the source data:

• filtered to populated places only (feature_class = 'P')
• restricted to RU, US, TR, CN
• restricted to name variants in ru, en, tr, zh
• dropped feature codes PPLH, PPLQ, PPLW, PPLX
• name variants grouped per place and joined into single document strings