Codebase analysis: fix 5 runtime bugs and create missing src/data package

[Copilot]

Full analysis of the Face Analysis AI V6 codebase. Found and fixed 5 bugs that would cause crashes or silent training failures, plus created a missing module that made every main entry point unrunnable.

Bugs Fixed

Critical: src/data/ package missing (ModuleNotFoundError)

predict.py, eval_multitask_proper.py, train_multitask_v3.py, and scripts/debug_predictions_v2.py all import from src.data.dataset — the package simply didn't exist. Created src/data/dataset.py with:

• FaceAnalysisDataset — multi-task dataset reading the build_multitask_annotations.py JSON format (shape, eye, brow, lip, age, gender, landmarks, Monk skin scale)
• extract_hsv_histogram_np — normalised 48-dim HSV histogram used by SkinTower
• get_train_transforms / get_val_transforms

Also fixed .gitignore — data/ glob was suppressing the new src/data/ source package.

Critical: SkinTower called with wrong arity (TypeError)

train_multitask_v3.py called self.model.skin_tone_head(detached_features) but SkinTower.forward requires (bb_features, hsv_histogram):

# before — TypeError at first training step
skin_tone_logits = self.model.skin_tone_head(detached_features)

# after
hsv_placeholder = torch.zeros(detached_features.shape[0], 48, device=detached_features.device)
skin_tone_logits = self.model.skin_tone_head(detached_features, hsv_placeholder)

High: skin_tone_head excluded from optimizer param groups

get_optimizer_param_groups() in FaceAnalysisModel listed every head except skin_tone_head, so its weights never received gradient updates when using FaceAnalysisLightningModule. Added list(self.skin_tone_head.parameters()) to head_params.

High: Wrong LOSS_WEIGHTS key names in MultiTaskLoss (KeyError)

losses.py looked up weights['shape'], weights['features'], weights['skin'] but LOSS_WEIGHTS in config.py uses face_shape_weight, features_weight, skin_tone_weight.

Low: Dead computation in FaceAnalysisModel.forward()

fused = self._get_fused_features(features, geometric_ratios) was computed on every forward pass and immediately discarded — the face shape head calls it internally. Removed.

Documentation

Added CODEBASE_ANALYSIS.md covering architecture (all 14 prediction heads, data flow, training phases), dataset sources, all bugs found, performance benchmarks, and known remaining limitations.

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[Krishna-Modi12]

Fixed