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Transformer Self-Attention From Scratch
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Transformer Self-Attention From Scratch

HardPython

Problem

Implement a basic version of a transformer's self-attention mechanism from scratch.

Implement scaled dot-product attention for query, key, and value matrices represented as nested lists. Return the attention output, applying an optional boolean mask where False entries are excluded. Use a numerically stable softmax and scale scores by the key dimension.

Constraints

  • 1 <= len(query) <= 256
  • 1 <= len(key) == len(value) <= 256
  • 1 <= len(query[0]) == len(key[0]) <= 128
  • 1 <= len(value[0]) <= 128
  • All rows in each matrix have consistent dimensions
  • If provided, mask has shape len(query) by len(key) and contains booleans
  • At least one position in every query mask row is True

Function Signature

def self_attention(query, key, value, mask=None):
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