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Deep Learning

Machine learning using neural networks with many layers — the approach behind nearly every recent AI breakthrough.

Reading level: Curious
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When not to use it

  • On small or tabular data. Deep learning's advantage shows up with scale and unstructured input. Below that, it's a slower, hungrier way to do worse.
  • When compute or latency is tight. A model that needs a GPU per request is an architecture decision with a bill attached.
  • When you need to explain the decision. Depth and interpretability trade against each other, and no amount of saliency mapping fully closes that gap.

Reach for something else instead

  • Gradient boosting for tabular problems — still the state of the art, still faster.
  • Classical CV/NLP for constrained tasks in controlled conditions.
  • A pretrained model via API instead of training your own. Most teams don't need to train anything.

Sources & further reading

  • LeCun, Bengio & Hinton (2015), Deep Learning (Nature) — the field's own account of itself.
  • Goodfellow, Bengio & Courville, Deep Learning — the textbook, free online.
  • Grinsztajn, Oyallon & Varoquaux (2022), Why do tree-based models still outperform deep learning on tabular data? — the honest limit.

Primary sources, listed so you can check the claims on this page rather than take them on trust.

Where people go wrong

  • Reaching for deep learning because it's the interesting option, not the fitting one.
  • Ignoring inference cost during model selection, then discovering the economics after the demo.
  • Assuming more layers means more understanding. It means more capacity to memorise.

At a glance

FieldFoundations
Core ideamany-layered neural networks
Key powerlearns features from raw data
Enabled bydata + GPUs + architecture advances
DifficultyBeginner → Intermediate
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