14_07_expt/model.py

"""Train a figure-skating action classifier on the pipeline's (T=64, 94)-feature tensors.

Architecture ported from training/cnn_lstm_attention.py (Keras): a Conv1D residual backbone,
a stack of multi-head self-attention blocks, temporal pooling, and a deep GELU dense head.
Kept deliberately simple on the training-loop side (Adam + CrossEntropy + val-based best-model
selection). Metrics (precision / recall / F1) come from scikit-learn.

LABEL CONSISTENCY (the thing that must not break):
    The pipeline saves integer labels that are *exactly* labels.TAXONOMY indices (0..27).
    This model's output layer has num_classes = len(TAXONOMY) units, so output unit i is, by
    construction, the score for TAXONOMY[i]. No compaction / remapping is done anywhere, so
    argmax(logits) is directly a TAXONOMY index. Assertions below enforce this before training.

Usage:
    python model.py                 # train on /data/processed_500
    python model.py --data-dir DIR  # train on another processed dir
    python model.py --smoke         # self-test the plumbing on synthetic data (no real data needed)
"""

from __future__ import annotations

import argparse
import json
import pickle
from pathlib import Path

import numpy as np
import torch
import torch.nn as nn
import torch.nn.functional as F
from sklearn.metrics import (
    accuracy_score,
    classification_report,
    confusion_matrix,
    f1_score,
    precision_recall_fscore_support,
)
from sklearn.utils.class_weight import compute_class_weight
from torch.utils.data import DataLoader, TensorDataset

try:
    from . import labels as labels_mod
except ImportError:
    import labels as labels_mod


# ---------------------------------------------------------------------------
# Config
# ---------------------------------------------------------------------------

DEFAULT_DATA_DIR = "/data/processed_500"
EPOCHS = 100
BATCH_SIZE = 64
LEARNING_RATE = 5e-4       # lowered from 1e-3: the raw velocity features are heavy-tailed (|v|~960)
WEIGHT_DECAY = 1e-4
GRAD_CLIP = 1.0            # clip grad norm; prevents rare-class / heavy-tail gradient spikes -> NaN
MAX_CLASS_WEIGHT = 5.0    # cap balanced class weights (singletons would otherwise get ~18x)
EARLY_STOP_PATIENCE = 20
SEED = 42
DEVICE = "cuda" if torch.cuda.is_available() else "cpu"


# ---------------------------------------------------------------------------
# Model (ported from training/cnn_lstm_attention.py)
# ---------------------------------------------------------------------------


class ConvBlock(nn.Module):
    """Conv1D + BN + Dropout with a (projected) residual connection. Input/return: (B, C, T)."""

    def __init__(self, in_ch: int, out_ch: int, kernel: int, dropout: float = 0.15):
        super().__init__()
        self.shortcut = nn.Conv1d(in_ch, out_ch, 1) if in_ch != out_ch else nn.Identity()
        self.conv = nn.Conv1d(in_ch, out_ch, kernel, padding="same")
        self.bn = nn.BatchNorm1d(out_ch)
        self.drop = nn.Dropout(dropout)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        y = F.relu(self.conv(x))
        y = self.drop(self.bn(y))
        return self.shortcut(x) + y


class AttnBlock(nn.Module):
    """Multi-head self-attention with residual + LayerNorm + Dropout. Input/return: (B, T, D)."""

    def __init__(self, dim: int = 384, heads: int = 8, attn_dropout: float = 0.1, dropout: float = 0.2):
        super().__init__()
        self.mha = nn.MultiheadAttention(dim, heads, dropout=attn_dropout, batch_first=True)
        self.norm = nn.LayerNorm(dim)
        self.drop = nn.Dropout(dropout)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        attn, _ = self.mha(x, x, x, need_weights=False)
        return self.drop(self.norm(x + attn))


class DenseBlock(nn.Module):
    """Linear + GELU + LayerNorm + BatchNorm + Dropout. Input/return: (B, features)."""

    def __init__(self, in_f: int, out_f: int, dropout: float):
        super().__init__()
        self.fc = nn.Linear(in_f, out_f)
        self.ln = nn.LayerNorm(out_f)
        self.bn = nn.BatchNorm1d(out_f)
        self.drop = nn.Dropout(dropout)

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        x = F.gelu(self.fc(x))
        return self.drop(self.bn(self.ln(x)))


class SkatingActionClassifier(nn.Module):
    """(B, T, F) sequence of skeleton features -> (B, num_classes) class logits."""

    def __init__(self, in_features: int, num_classes: int):
        super().__init__()
        # Conv backbone (expects channels-first (B, F, T))
        self.stem = nn.Conv1d(in_features, 128, 3, padding="same")
        self.stem_bn = nn.BatchNorm1d(128)
        self.cb1 = ConvBlock(128, 192, 3)
        self.cb2 = ConvBlock(192, 256, 3)
        self.cb3 = ConvBlock(256, 384, 5)
        # Attention stack (operates on (B, T, 384))
        self.attn = nn.ModuleList([AttnBlock(384, heads=8) for _ in range(3)])
        # Deep classification head (temporal mean-pool -> 384). The reference concatenated two
        # identical mean-pools (768); a single mean-pool carries the same information.
        self.head = nn.Sequential(
            DenseBlock(384, 1024, 0.5),
            DenseBlock(1024, 512, 0.4),
            DenseBlock(512, 256, 0.3),
            nn.LayerNorm(256),
        )
        self.out = nn.Linear(256, num_classes)  # logits; softmax handled by CrossEntropyLoss

    def forward(self, x: torch.Tensor) -> torch.Tensor:
        x = x.transpose(1, 2)                      # (B, F, T)
        x = F.relu(self.stem(x))
        x = self.stem_bn(x)
        x = self.cb3(self.cb2(self.cb1(x)))        # (B, 384, T)
        x = x.transpose(1, 2)                      # (B, T, 384)
        for blk in self.attn:
            x = blk(x)
        x = x.mean(dim=1)                          # temporal average pool -> (B, 384)
        return self.out(self.head(x))


# ---------------------------------------------------------------------------
# Data
# ---------------------------------------------------------------------------


def _load_pickle(path: Path):
    with path.open("rb") as f:
        return pickle.load(f)


def load_split(data_dir: Path, split: str) -> tuple[np.ndarray, np.ndarray]:
    X = np.asarray(_load_pickle(data_dir / f"{split}_features.pkl"), dtype=np.float32)
    y = np.asarray(_load_pickle(data_dir / f"{split}_labels.pkl"), dtype=np.int64)
    return X, y


def resolve_num_classes(data_dir: Path) -> int:
    """num_classes comes from the taxonomy; cross-checked against the pipeline's metadata.json."""
    n = len(labels_mod.TAXONOMY)
    meta_path = data_dir / "metadata.json"
    if meta_path.exists():
        meta_n = int(json.loads(meta_path.read_text())["num_classes"])
        assert meta_n == n, (
            f"metadata num_classes={meta_n} disagrees with labels.TAXONOMY ({n}). "
            "The pipeline and the model are using different taxonomies -- refusing to train."
        )
    return n


def assert_label_consistency(num_classes: int, *label_arrays: np.ndarray) -> None:
    """Every saved label must be a valid TAXONOMY index; guarantees softmax<->label alignment."""
    for y in label_arrays:
        if y.size == 0:
            continue
        lo, hi = int(y.min()), int(y.max())
        assert 0 <= lo and hi < num_classes, (
            f"label out of range: found [{lo}, {hi}] but valid TAXONOMY indices are "
            f"[0, {num_classes - 1}]. Softmax index space would not match the labels."
        )


# ---------------------------------------------------------------------------
# Train / evaluate
# ---------------------------------------------------------------------------


def run_epoch(model, loader, criterion, optimizer=None) -> tuple[float, float]:
    train = optimizer is not None
    model.train(train)
    total_loss, correct, n = 0.0, 0, 0
    for xb, yb in loader:
        xb, yb = xb.to(DEVICE), yb.to(DEVICE)
        with torch.set_grad_enabled(train):
            logits = model(xb)
            loss = criterion(logits, yb)
            if train:
                if not torch.isfinite(loss):  # defensive: never step on a non-finite loss
                    continue
                optimizer.zero_grad()
                loss.backward()
                torch.nn.utils.clip_grad_norm_(model.parameters(), GRAD_CLIP)
                optimizer.step()
        total_loss += loss.item() * xb.size(0)
        correct += (logits.argmax(1) == yb).sum().item()
        n += xb.size(0)
    return total_loss / n, correct / n


@torch.no_grad()
def predict(model, X: np.ndarray) -> np.ndarray:
    model.eval()
    out = []
    for i in range(0, len(X), 256):
        xb = torch.from_numpy(X[i : i + 256]).to(DEVICE)
        out.append(model(xb).argmax(1).cpu().numpy())
    return np.concatenate(out) if out else np.array([], dtype=np.int64)


def report_metrics(y_true: np.ndarray, y_pred: np.ndarray, taxonomy: dict) -> dict:
    num_classes = len(taxonomy)
    class_ids = list(range(num_classes))
    names = [taxonomy[i] for i in class_ids]
    acc = accuracy_score(y_true, y_pred)
    p_macro, r_macro, f_macro, _ = precision_recall_fscore_support(
        y_true, y_pred, labels=class_ids, average="macro", zero_division=0
    )
    p_w, r_w, f_w, _ = precision_recall_fscore_support(
        y_true, y_pred, labels=class_ids, average="weighted", zero_division=0
    )
    print("\n" + "=" * 72)
    print("TEST METRICS")
    print("=" * 72)
    print(f"accuracy                 : {acc:.4f}")
    print(f"precision (macro/weighted): {p_macro:.4f} / {p_w:.4f}")
    print(f"recall    (macro/weighted): {r_macro:.4f} / {r_w:.4f}")
    print(f"f1        (macro/weighted): {f_macro:.4f} / {f_w:.4f}")
    present = sorted(set(y_true.tolist()) | set(y_pred.tolist()))
    print("\nper-class report (classes present in test true/pred only):")
    print(
        classification_report(
            y_true, y_pred,
            labels=present,
            target_names=[taxonomy[i] for i in present],
            zero_division=0,
            digits=3,
        )
    )
    return {
        "accuracy": acc,
        "precision_macro": p_macro, "recall_macro": r_macro, "f1_macro": f_macro,
        "precision_weighted": p_w, "recall_weighted": r_w, "f1_weighted": f_w,
    }


def train(data_dir: Path, coarse: bool = False) -> dict:
    torch.manual_seed(SEED)
    np.random.seed(SEED)

    fine_n = resolve_num_classes(data_dir)  # 28, cross-checked against metadata.json
    taxonomy = labels_mod.COARSE_TAXONOMY if coarse else labels_mod.TAXONOMY
    num_classes = len(taxonomy)
    Xtr, ytr = load_split(data_dir, "train")
    Xva, yva = load_split(data_dir, "val")
    Xte, yte = load_split(data_dir, "test")
    # Saved labels are always fine TAXONOMY indices -> validate in that space first, then coarsen.
    # This keeps the whole chain consistent: saved fine idx -> FINE_TO_COARSE_IDX -> softmax unit.
    assert_label_consistency(fine_n, ytr, yva, yte)
    if coarse:
        def coarsen(y):
            return np.array([labels_mod.FINE_TO_COARSE_IDX[int(v)] for v in y], dtype=np.int64)
        ytr, yva, yte = coarsen(ytr), coarsen(yva), coarsen(yte)
        assert_label_consistency(num_classes, ytr, yva, yte)
    in_features = Xtr.shape[-1]
    print(f"label space: {'COARSE action-level' if coarse else 'FINE'} | {num_classes} classes")

    # Per-feature standardization from TRAIN stats only (applied to all splits + stored for
    # inference). The velocity block is heavy-tailed (|v| up to ~960 vs coords ~1); feeding it raw
    # blows up activations -> NaN. z-scoring brings every feature onto a comparable scale.
    mu = Xtr.mean(axis=(0, 1), keepdims=True)
    sd = Xtr.std(axis=(0, 1), keepdims=True) + 1e-6
    Xtr = (Xtr - mu) / sd
    Xva = (Xva - mu) / sd
    Xte = (Xte - mu) / sd

    print(f"device={DEVICE} | num_classes={num_classes} (== len(taxonomy)) | in_features={in_features}")
    print(f"shapes: train={Xtr.shape} val={Xva.shape} test={Xte.shape}")
    print(f"standardized features: train |max|={np.abs(Xtr).max():.1f} (was heavy-tailed pre-scaling)")
    print(f"train classes present: {sorted(set(ytr.tolist()))}")

    # class-balanced loss weights (train distribution), capped so singleton classes don't get
    # ~18x weight and destabilize training. "proper" imbalance handling without the spikes.
    present = np.unique(ytr)
    cw = np.clip(compute_class_weight(class_weight="balanced", classes=present, y=ytr),
                 None, MAX_CLASS_WEIGHT)
    weight = torch.ones(num_classes)
    for c, w in zip(present, cw):
        weight[int(c)] = float(w)
    criterion = nn.CrossEntropyLoss(weight=weight.to(DEVICE))

    model = SkatingActionClassifier(in_features, num_classes).to(DEVICE)
    n_params = sum(p.numel() for p in model.parameters())
    print(f"model params: {n_params/1e6:.2f}M")
    optimizer = torch.optim.Adam(model.parameters(), lr=LEARNING_RATE, weight_decay=WEIGHT_DECAY)

    tr_loader = DataLoader(
        TensorDataset(torch.from_numpy(Xtr), torch.from_numpy(ytr)),
        batch_size=BATCH_SIZE, shuffle=True, drop_last=False,
    )
    va_loader = DataLoader(
        TensorDataset(torch.from_numpy(Xva), torch.from_numpy(yva)),
        batch_size=BATCH_SIZE, shuffle=False,
    )

    best_val_f1, best_state, since_improved = -1.0, None, 0
    for epoch in range(1, EPOCHS + 1):
        tr_loss, tr_acc = run_epoch(model, tr_loader, criterion, optimizer)
        va_loss, va_acc = run_epoch(model, va_loader, criterion)
        va_f1 = f1_score(yva, predict(model, Xva), labels=list(range(num_classes)),
                         average="macro", zero_division=0)
        if va_f1 > best_val_f1:
            best_val_f1, since_improved = va_f1, 0
            best_state = {k: v.detach().cpu().clone() for k, v in model.state_dict().items()}
        else:
            since_improved += 1
        if epoch % 5 == 0 or epoch == 1:
            print(f"epoch {epoch:3d} | train loss {tr_loss:.3f} acc {tr_acc:.3f} "
                  f"| val loss {va_loss:.3f} acc {va_acc:.3f} f1(macro) {va_f1:.3f}")
        if since_improved >= EARLY_STOP_PATIENCE:
            print(f"early stop at epoch {epoch} (no val-F1 improvement for {EARLY_STOP_PATIENCE})")
            break

    if best_state is not None:
        model.load_state_dict(best_state)
    print(f"\nrestored best model (val macro-F1 = {best_val_f1:.3f})")

    metrics = report_metrics(yte, predict(model, Xte), taxonomy)
    ckpt_name = "model_coarse.pt" if coarse else "model.pt"
    torch.save({"state_dict": model.state_dict(), "num_classes": num_classes,
                "in_features": in_features, "taxonomy": taxonomy, "coarse": coarse,
                "feature_mean": mu, "feature_std": sd},  # standardizer for inference consistency
               data_dir / ckpt_name)
    print(f"\nsaved model -> {data_dir / ckpt_name}")
    return metrics


def smoke() -> None:
    """Validate the full plumbing on synthetic data shaped exactly like the pipeline output."""
    print("SMOKE: synthetic (N,64,94) data, labels in TAXONOMY index space")
    num_classes = len(labels_mod.TAXONOMY)
    rng = np.random.default_rng(0)
    X = rng.standard_normal((40, 64, 94)).astype(np.float32)
    y = rng.integers(0, num_classes, size=40).astype(np.int64)
    assert_label_consistency(num_classes, y)
    model = SkatingActionClassifier(94, num_classes).to(DEVICE)
    logits = model(torch.from_numpy(X[:4]).to(DEVICE))
    assert logits.shape == (4, num_classes), logits.shape
    loss = nn.CrossEntropyLoss()(logits, torch.from_numpy(y[:4]).to(DEVICE))
    loss.backward()
    print(f"forward OK: logits {tuple(logits.shape)} | loss {loss.item():.3f} | backward OK")
    print(f"num_classes={num_classes} matches softmax units; argmax range in [0,{num_classes-1}]")
    print("SMOKE PASSED")


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--data-dir", type=Path, default=Path(DEFAULT_DATA_DIR))
    parser.add_argument("--coarse", action="store_true",
                        help="collapse jump rotations into action-level classes (11 instead of 28)")
    parser.add_argument("--smoke", action="store_true", help="self-test on synthetic data")
    args = parser.parse_args()
    if args.smoke:
        smoke()
        return 0
    if not (args.data_dir / "train_features.pkl").exists():
        raise SystemExit(f"No processed data at {args.data_dir}. Run the pipeline first.")
    train(args.data_dir, coarse=args.coarse)
    return 0


if __name__ == "__main__":
    raise SystemExit(main())