TASK 1 — KV CACHE BENCHMARK
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 src_len   standard(s)   cached(s)   speedup   encoder%   mem-save%
      16         3.431       3.512     0.98x     133.1%       50.0%
          source-mem before=0.070MB  after=0.035MB
      32         3.626       3.555     1.02x      36.8%       50.0%
          source-mem before=0.141MB  after=0.070MB
      64         3.585       3.701     0.97x      53.3%       50.0%
          source-mem before=0.281MB  after=0.141MB




  Encoder cost = % of one full forward pass
  Speedup = standard_time / cached_time
  Expected: speedup ≈ 1 / (1 - encoder_pct/100 * (T-1)/T)

  SUMMARY
  -------
  src_len=16: 0.98x speedup (-2.4% time saved, encoder was 133.1% of total, estimated memory change 50.0%)
  src_len=32: 1.02x speedup (1.9% time saved, encoder was 36.8% of total, estimated memory change 50.0%)
  src_len=64: 0.97x speedup (-3.2% time saved, encoder was 53.3% of total, estimated memory change 50.0%)