Large-Scale Recommendation System: Ensembles, Overfitting, Metrics, Architectures, and Optimization
Context
You are designing a large-scale recommendation/ranking model (millions–billions of events, highly imbalanced positives) and must choose and evaluate ensemble models. You also need to understand modern deep architectures and training stability.
Tasks
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Compare Random Forest (RF) vs. XGBoost in terms of:
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Bias–variance trade-off
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Training speed and scalability
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Interpretability
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Define overfitting. List at least three techniques you would apply to reduce it in this recommendation context.
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Describe at least four evaluation metrics you would use, and when each is preferable.
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Explain how LoRA adapts large transformers. Contrast CNN, RNN, and Transformer architectures; include why attention helps with long-range dependencies.
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What causes gradient vanishing/exploding, and how do batch normalization, residual connections, or careful initialization mitigate it?