Tabpfn Explore

Core context: See tabpfn-core for behavior rules, workflow principles, and project conventions. Preprocessing rules: See data-requirements.md for what TabPFN handles natively vs. what needs preparation. API limits: See api-setup.md for budget checks.

1. Competition Reconnaissance

Before touching data, gather and document context:

• Read the competition description, evaluation metric, data description, and rules thoroughly.
• Read top-voted discussion posts and public notebooks for domain insights and known pitfalls.
• Identify: task type (binary classification, multi-class, regression), exact evaluation metric, dataset size (rows × columns), whether test labels are hidden, and any temporal/grouped structure.
• Check for leakage vectors: does the test set overlap with training? Are there features derived from the target or from future data?
• Write a concise summary to notes/competition_overview.md covering: metric, task type, dataset dimensions, key risks, and initial hypotheses.

2. EDA Essentials

Profile the data systematically. Focus on findings that change modeling decisions.

import pandas as pd
import numpy as np

train = pd.read_csv("data/raw/train.csv")
test = pd.read_csv("data/raw/test.csv")

print(f"Train: {train.shape}, Test: {test.shape}")
print(f"Total cells (train+test): {(len(train) + len(test)) * train.shape[1]:,}")
print(train.dtypes.value_counts())

# Missing values
missing = train.isnull().sum()
print(missing[missing > 0].sort_values(ascending=False))

# Target distribution
print(train["target"].describe())
print(train["target"].value_counts(normalize=True))

# Cardinality of categoricals
for col in train.select_dtypes(include=["object", "category"]).columns:
    print(f"{col}: {train[col].nunique()} unique values")

Checklist — flag each as ✅ done or ⚠️ issue found:

3. Adversarial Validation

Train a classifier to distinguish train from test rows. If AUC > 0.8, there is meaningful distribution shift — investigate which features drive the separation and decide whether to address it.

from sklearn.model_selection import cross_val_score
from sklearn.ensemble import RandomForestClassifier

combined = pd.concat([train.drop(columns=["target"]), test], ignore_index=True)
labels = np.array([0]*len(train) + [1]*len(test))
adv_auc = cross_val_score(
    RandomForestClassifier(n_estimators=100, random_state=42),
    combined.select_dtypes(include="number"), labels, cv=5, scoring="roc_auc"
).mean()
print(f"Adversarial Validation AUC: {adv_auc:.4f}")
# > 0.8 → meaningful shift, investigate
# 0.6-0.8 → moderate shift, note it
# < 0.6 → train/test are similar, good

4. API Cell Budget Check

Always run before any TabPFN call. See api-setup.md for the full reference.

n_train, n_test = len(train), len(test)
n_cols = train.drop(columns=["target"]).shape[1]
total_cells = (n_train + n_test) * n_cols
print(f"Total cells: {total_cells:,} / 20,000,000")
print("✅ OK" if total_cells < 20_000_000 else "EXCEEDS LIMIT — subsample or batching required")

5. Cross-Validation Scheme

Establish the CV scheme before any modeling. This is the source of truth for all experiments.

from sklearn.model_selection import StratifiedKFold, KFold

N_FOLDS = 5
SEED = 42

# Classification — stratified to preserve class balance per fold
folds = list(StratifiedKFold(n_splits=N_FOLDS, shuffle=True, random_state=SEED).split(X_train, y_train))

# Regression — standard k-fold
folds = list(KFold(n_splits=N_FOLDS, shuffle=True, random_state=SEED).split(X_train))

# Time-based: use TimeSeriesSplit
# Grouped: use GroupKFold with the appropriate group column

Rules:

• The CV scheme MUST mirror the competition's test distribution.
• Save the folds list and reuse the exact same splits for every single model. Non-negotiable for fair comparison and stacking.
• Record fold-level scores (not just the mean) to assess variance.

6. Output Deliverables

At the end of this phase, the following must exist:

1. notes/competition_overview.md — competition summary and key findings
2. Clean X_train, y_train, X_test DataFrames ready for TabPFN (see data-requirements.md)
3. folds — CV split indices reusable across all models
4. API budget check passed (or subsampling plan if not)
5. List of identified issues: leakage, shift, imbalance, high-cardinality, etc.
6. Feature lists: id_cols, drop_cols, categorical_cols, numeric_cols