What is the memory cost of HyperLogLog?
Fixed at 12 KB regardless of cardinality. It maintains 16,384 registers (one per possible 14-bit hash prefix), each storing the maximum leading-zero count observed for that prefix. This tiny footprint works from millions to billions of unique items.
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Count Billions in 12 KilobytesHyperLogLog estimates cardinality by reading leading zeros in hashed values, trading 1% error for fixed memory.
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