doc: clarify CRollingBloomFilter size estimate
(cherry picked from commit d9141a0002bb508b2e94e206a1bd28ef8f97ffde)
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src/bloom.h
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src/bloom.h
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@ -102,7 +102,18 @@ public:
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* insert()'ed ... but may also return true for items that were not inserted.
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*
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* It needs around 1.8 bytes per element per factor 0.1 of false positive rate.
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* (More accurately: 3/(log(256)*log(2)) * log(1/fpRate) * nElements bytes)
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* For example, if we want 1000 elements, we'd need:
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* - ~1800 bytes for a false positive rate of 0.1
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* - ~3600 bytes for a false positive rate of 0.01
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* - ~5400 bytes for a false positive rate of 0.001
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*
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* If we make these simplifying assumptions:
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* - logFpRate / log(0.5) doesn't get rounded or clamped in the nHashFuncs calculation
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* - nElements is even, so that nEntriesPerGeneration == nElements / 2
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*
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* Then we get a more accurate estimate for filter bytes:
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*
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* 3/(log(256)*log(2)) * log(1/fpRate) * nElements
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*/
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class CRollingBloomFilter
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{
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