scripts/cp4_classical.py

"""CP-4: Classical baselines on gold-test.

Baselines:
  - Random  (uniform 0/1)
  - Majority (always predict positive class)
  - RuleCue (any of: would, wish, should, could, need, please, if, hope, recommend, suggest, must, have to)
  - TF-IDF + Logistic Regression
  - TF-IDF + Linear SVM

Trains on gold_train (3-seed bootstrap), evaluates on gold_test.
Saves to work/results/classical.json
"""
from __future__ import annotations
import json, re
from pathlib import Path
import numpy as np
import pandas as pd
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.linear_model import LogisticRegression
from sklearn.svm import LinearSVC
from sklearn.metrics import classification_report, f1_score, precision_score, recall_score, accuracy_score, confusion_matrix

ROOT = Path("/home/aniket/praxis-benchmark")
WORK = ROOT / "work"
DATA = WORK / "data"
RES = WORK / "results"

RULE_PATTERN = re.compile(
    r"\b(would|wish(?:ed)?|should|could|need(?:s|ed)?|must|have to|please|hope(?:d)?|recommend(?:s|ed|ing)?|suggest(?:s|ed|ing)?|if|why don't|why not|why\s*(can't|aren't|isn't|doesn't|don't))\b",
    re.IGNORECASE
)


def load_splits():
    train = pd.read_csv(DATA / "gold_train.csv", low_memory=False)
    dev = pd.read_csv(DATA / "gold_dev.csv", low_memory=False)
    test = pd.read_csv(DATA / "gold_test.csv", low_memory=False)
    for df in (train, dev, test):
        df['text'] = df['text'].fillna('').astype(str)
        df['label'] = df['is_suggestion'].astype(int)
    return train, dev, test


def metrics(y_true, y_pred, label='pos'):
    return {
        'accuracy': float(accuracy_score(y_true, y_pred)),
        'macro_f1': float(f1_score(y_true, y_pred, average='macro', zero_division=0)),
        'pos_f1': float(f1_score(y_true, y_pred, pos_label=1, zero_division=0)),
        'pos_precision': float(precision_score(y_true, y_pred, pos_label=1, zero_division=0)),
        'pos_recall': float(recall_score(y_true, y_pred, pos_label=1, zero_division=0)),
        'confusion_matrix': confusion_matrix(y_true, y_pred).tolist(),
    }


def run_random(test, seed):
    rng = np.random.default_rng(seed)
    y_pred = rng.integers(0, 2, size=len(test))
    return metrics(test['label'].values, y_pred)


def run_majority(test):
    y_pred = np.ones(len(test), dtype=int)  # positive is majority by construction
    return metrics(test['label'].values, y_pred)


def run_rule(test):
    y_pred = test['text'].str.contains(RULE_PATTERN).astype(int).values
    return metrics(test['label'].values, y_pred)


def run_tfidf(train, test, model_kind='lr', seed=42):
    vec = TfidfVectorizer(ngram_range=(1, 3), min_df=2, max_df=0.9, sublinear_tf=True,
                          analyzer='word', max_features=80_000)
    X_train = vec.fit_transform(train['text'])
    X_test = vec.transform(test['text'])
    if model_kind == 'lr':
        clf = LogisticRegression(C=1.0, max_iter=2000, random_state=seed, n_jobs=-1)
    else:
        clf = LinearSVC(C=1.0, random_state=seed, max_iter=3000)
    clf.fit(X_train, train['label'])
    y_pred = clf.predict(X_test)
    m = metrics(test['label'].values, y_pred)
    # per-form F1 if test contains form info — we'll also evaluate per-form via the span_only positives
    return m, clf, vec


def per_form_f1(test, y_pred):
    res = {}
    for form in ['Direct imperative', 'Modal/deontic', 'Conditional', 'Optative',
                 'Interrogative', 'Comparative']:
        mask = (test['tier1_form'] == form) & (test['label'] == 1)
        # F1 on positives of this form: this is recall actually (since form is only set for positives)
        if mask.sum() > 0:
            res[form] = float((y_pred[mask.values] == 1).mean())
    return res


def main():
    print("=" * 70)
    print("CP-4: Classical baselines")
    print("=" * 70)
    train, dev, test = load_splits()
    print(f"Train {len(train)} / Dev {len(dev)} / Test {len(test)}; train pos rate {train['label'].mean():.3f}")

    results = {}
    seeds = [13, 42, 137]

    # Random
    rand_runs = [run_random(test, s) for s in seeds]
    results['Random'] = aggregate(rand_runs)

    # Majority
    results['Majority(pos)'] = run_majority(test)

    # Rule
    results['Rule(modal/wish/should/...)'] = run_rule(test)
    rule_pred = test['text'].str.contains(RULE_PATTERN).astype(int).values
    results['Rule(modal/wish/should/...)']['per_form_recall'] = per_form_f1(test, rule_pred)

    # TF-IDF + LR
    print("\nTF-IDF + LR (3 seeds)...")
    lr_runs = []
    for s in seeds:
        m, clf, vec = run_tfidf(train, test, 'lr', s)
        lr_runs.append(m)
    results['TFIDF+LR'] = aggregate(lr_runs)
    # Keep one model's per-form recall
    _, clf, vec = run_tfidf(train, test, 'lr', 42)
    y_pred = clf.predict(vec.transform(test['text']))
    results['TFIDF+LR']['per_form_recall'] = per_form_f1(test, y_pred)

    # TF-IDF + SVM
    print("TF-IDF + SVM (3 seeds)...")
    svm_runs = []
    for s in seeds:
        m, _, _ = run_tfidf(train, test, 'svm', s)
        svm_runs.append(m)
    results['TFIDF+SVM'] = aggregate(svm_runs)
    _, clf, vec = run_tfidf(train, test, 'svm', 42)
    y_pred = clf.predict(vec.transform(test['text']))
    results['TFIDF+SVM']['per_form_recall'] = per_form_f1(test, y_pred)

    print("\n--- Results ---")
    for name, m in results.items():
        if 'macro_f1_mean' in m:
            print(f"{name:30s}  macro-F1 {m['macro_f1_mean']:.3f}±{m['macro_f1_std']:.3f}  pos-F1 {m['pos_f1_mean']:.3f}")
        else:
            print(f"{name:30s}  macro-F1 {m['macro_f1']:.3f}  pos-F1 {m['pos_f1']:.3f}")

    # Save
    with (RES / "classical.json").open("w") as f:
        json.dump(results, f, indent=2)
    print(f"\nSaved {RES}/classical.json")
    print("CP-4 DONE.")


def aggregate(runs):
    keys = ['accuracy', 'macro_f1', 'pos_f1', 'pos_precision', 'pos_recall']
    out = {}
    for k in keys:
        vals = [r[k] for r in runs]
        out[f'{k}_mean'] = float(np.mean(vals))
        out[f'{k}_std'] = float(np.std(vals))
    return out


if __name__ == '__main__':
    main()