Why it matters

Count sketch reduces bias in skewed streams. Better than Count-Min for heavy hitters.

Advertisement

The architecture

d rows × w counters.

Signed hash (+1/-1) added to counter.

Query = median across rows.

Count sketchSigned hash+1 or -1 per rowCountersd × wQuerymedian across rowsCharikar-Chen-Farach-Colton 2002; unbiased; better for heavy hitters
Count sketch.
Advertisement

How it works end to end

Charikar-Chen-Farach-Colton 2002.

Median estimator.

Unbiased.