Suggest Bloom filter sizing parameters — bloom_filter

Helpers that translate a target accuracy into Bloom filter constructor arguments for the num_bits/num_hashes sizing strategy. These compute the same values that bloom_filter() uses internally for the max_items/fpp sizing strategy, for callers who want to inspect or reuse them (for example, to create multiple compatible filters with an explicit seed).

Usage

bloom_filter_suggest_num_filter_bits(max_items, fpp)

bloom_filter_suggest_num_hashes(max_items, num_bits)

Arguments

max_items: Target maximum number of distinct items, a single positive whole number up to 2^53.
fpp: Target false-positive probability, a single number in (0, 1].
num_bits: Number of bits in the filter, a single positive whole number up to 2^53.

Value

A single number: bloom_filter_suggest_num_filter_bits() returns the suggested num_bits (a double, which may exceed .Machine$integer.max); bloom_filter_suggest_num_hashes() returns the suggested num_hashes (an integer).

Examples

num_bits <- bloom_filter_suggest_num_filter_bits(1000, 0.01)
num_hashes <- bloom_filter_suggest_num_hashes(1000, num_bits)
bf <- bloom_filter(num_bits = num_bits, num_hashes = num_hashes)