#!/usr/bin/env python3
"""Evaluate rankings per query: NDCG, MAP, MRR, ERR, precision@k, and whether model A really beats model B.
Input: CSV with query id, graded relevance label and one or more score columns (higher = ranked higher), e.g.
the predictions of several rankers on the same test documents: qid,label,bm25,lgbm_score,xgb_score.
Per score column (averaged over queries):
NDCG@k gain 2^label - 1 (--gain exp, the LightGBM/XGBoost/TREC default) or label (--gain linear, the
scikit-learn ndcg_score convention), log2 discount
MAP@k, MRR, P@k binary relevance: label >= --rel-min
ERR@k expected reciprocal rank (cascade model; graded labels)
Queries without any relevant document have undefined NDCG: --empty skip (default, excluded and counted),
one (LightGBM's convention: counts as 1.0) or zero. Score ties are broken pessimistically by default (lower
label first, so a constant or coarse score cannot look good); --ties input keeps file order within ties, which
reproduces LightGBM's own NDCG@k evaluation (rows in group order), --ties optimistic the upper bound.
Comparison (--baseline COLUMN): for every other column, the mean per-query NDCG@k difference with a
95% bootstrap CI over queries and a paired randomisation (sign-flip) test p-value (10,000 permutations,
seeded) - queries are the unit of analysis, not documents.
Usage:
python rank_eval.py ltr.csv --qid-col qid --label-col label --scores bm25 clicks score --k 5 10
python rank_eval.py preds.csv --scores lgbm xgb --baseline bm25 --k 10 --gain linear
python rank_eval.py preds.csv --scores model --k 10 --per-query worst.csv --json
Exit codes: 0 evaluated, 1 with --baseline when no model is significantly better (p < 0.05), 2 usage error.
"""
import argparse
import csv
import json
import math
import os
import random
import sys
from collections import defaultdict
sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
from _rank_metrics import average_precision, err, ndcg, precision, rank_by, reciprocal_rank # noqa: E402
def num(v):
try:
x = float(v)
return x if math.isfinite(x) else None
except (TypeError, ValueError):
return None
def per_query(groups, col, k, a, max_label):
out = {}
for q, docs in groups.items():
d = [(lab, s[col]) for lab, s in docs]
ranked = rank_by(d, a.ties)
nd = ndcg(ranked, k, a.gain)
if nd is None:
nd = {"skip": None, "one": 1.0, "zero": 0.0}[a.empty]
out[q] = {"ndcg": nd, "map": average_precision(ranked, k, a.rel_min), "mrr": reciprocal_rank(ranked, a.rel_min),
"p": precision(ranked, k, a.rel_min), "err": err(ranked, k, max_label)}
return out
def mean(xs):
xs = [x for x in xs if x is not None]
return sum(xs) / len(xs) if xs else None
def compare(base, other, seed=0, boots=2000, perms=10000):
qs = [q for q in base if base[q]["ndcg"] is not None and other[q]["ndcg"] is not None]
diffs = [other[q]["ndcg"] - base[q]["ndcg"] for q in qs]
n = len(diffs)
md = sum(diffs) / n
rng = random.Random(seed)
bs = sorted(sum(diffs[rng.randrange(n)] for _ in range(n)) / n for _ in range(boots))
ci = (bs[int(0.025 * boots)], bs[int(0.975 * boots) - 1])
obs = abs(md)
extreme = 0
for _ in range(perms):
s = sum(d if rng.random() < 0.5 else -d for d in diffs) / n
if abs(s) >= obs - 1e-15:
extreme += 1
return {"queries": n, "mean_diff": md, "ci": ci, "p": (extreme + 1) / (perms + 1),
"wins": sum(1 for d in diffs if d > 1e-12), "losses": sum(1 for d in diffs if d < -1e-12)}
def main():
ap = argparse.ArgumentParser(description="Evaluate rankings per query.", epilog=__doc__,
formatter_class=argparse.RawDescriptionHelpFormatter)
ap.add_argument("csv")
ap.add_argument("--qid-col", default="qid")
ap.add_argument("--label-col", default="label")
ap.add_argument("--scores", nargs="+", required=True)
ap.add_argument("--k", type=int, nargs="+", default=[10])
ap.add_argument("--gain", choices=["exp", "linear"], default="exp")
ap.add_argument("--rel-min", type=float, default=1)
ap.add_argument("--empty", choices=["skip", "one", "zero"], default="skip")
ap.add_argument("--ties", choices=["pessimistic", "input", "optimistic"], default="pessimistic",
help="order of documents with equal scores (input = file order, as LightGBM does)")
ap.add_argument("--baseline", help="score column to compare every other column against")
ap.add_argument("--per-query", help="write per-query NDCG@k (first k) for each column to this CSV")
ap.add_argument("--json", action="store_true")
a = ap.parse_args()
try:
with open(a.csv, newline="", encoding="utf-8") as f:
rows = list(csv.DictReader(f))
if not rows:
raise ValueError("no rows")
cols = [a.qid_col, a.label_col] + a.scores + ([a.baseline] if a.baseline else [])
miss = [c for c in cols if c not in rows[0]]
if miss:
raise ValueError(f"columns not found: {', '.join(miss)}")
groups = defaultdict(list)
for r in rows:
lab = num(r[a.label_col])
if lab is None:
raise ValueError("labels must be numeric")
groups[r[a.qid_col]].append((lab, {c: num(r[c]) if num(r[c]) is not None else -math.inf
for c in set(a.scores) | ({a.baseline} if a.baseline else set())}))
except (OSError, ValueError) as e:
print(f"error: {e}", file=sys.stderr)
return 2
max_label = max(lab for g in groups.values() for lab, _ in g)
columns = list(dict.fromkeys(([a.baseline] if a.baseline else []) + a.scores))
res = {"queries": len(groups), "gain": a.gain, "results": {}, "comparisons": {}}
pq_first = {}
for k in a.k:
res["results"][k] = {}
for c in columns:
pq = per_query(groups, c, k, a, max_label)
if k == a.k[0]:
pq_first[c] = pq
vals = list(pq.values())
res["results"][k][c] = {m: mean(v[m] for v in vals) for m in ("ndcg", "map", "mrr", "p", "err")}
res["results"][k][c]["evaluated"] = sum(1 for v in vals if v["ndcg"] is not None)
empty = sum(1 for g in groups.values() if not any(lab >= a.rel_min for lab, _ in g))
if a.baseline:
for c in a.scores:
if c != a.baseline:
res["comparisons"][c] = compare(pq_first[a.baseline], pq_first[c])
if a.per_query:
with open(a.per_query, "w", newline="", encoding="utf-8") as f:
w = csv.writer(f)
w.writerow(["qid"] + [f"{c}_ndcg@{a.k[0]}" for c in columns])
for q in groups:
w.writerow([q] + [pq_first[c][q]["ndcg"] for c in columns])
if a.json:
print(json.dumps(res, indent=2, default=str))
else:
print(f"queries: {len(groups)} gain: {a.gain} relevant: label >= {a.rel_min:g} "
f"queries without relevant documents: {empty} ({'excluded' if a.empty == 'skip' else 'NDCG=' + a.empty})")
for k in a.k:
print(f"\n@{k}")
print(f"{'model':<20} {'NDCG':>8} {'MAP':>8} {'MRR':>8} {'P':>8} {'ERR':>8}")
for c, v in sorted(res["results"][k].items(), key=lambda kv: -(kv[1]["ndcg"] or 0)):
print(f"{c:<20} " + " ".join(f"{(v[m] if v[m] is not None else float('nan')):>8.4f}"
for m in ("ndcg", "map", "mrr", "p", "err")))
if res["comparisons"]:
print(f"\npaired comparison vs {a.baseline} (NDCG@{a.k[0]}, per query):")
for c, d in res["comparisons"].items():
verdict = "better" if d["p"] < 0.05 and d["mean_diff"] > 0 else (
"worse" if d["p"] < 0.05 else "no significant difference")
print(f" {c:<18} diff {d['mean_diff']:+.4f} [95% CI {d['ci'][0]:+.4f}, {d['ci'][1]:+.4f}] "
f"p = {d['p']:.4f} wins/losses {d['wins']}/{d['losses']} -> {verdict}")
if a.baseline and res["comparisons"]:
if not any(d["p"] < 0.05 and d["mean_diff"] > 0 for d in res["comparisons"].values()):
return 1
return 0
if __name__ == "__main__":
sys.exit(main())
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