60 lines
1.8 KiB
Erlang
60 lines
1.8 KiB
Erlang
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%% Test performance and accuracy of rice-encoded bloom filters
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%%
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%% Calling check_negative(2048, 1000000) should return about 122 false
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%% positives in around 11 seconds, with a size below 4KB
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%%
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%% The equivalent positive check is check_positive(2048, 488) and this
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%% should take around 6 seconds.
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%%
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%% So a blooom with 2048 members should support o(100K) checks per second
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%% on a modern CPU, whilst requiring 2 bytes per member.
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-module(rice_test).
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-export([check_positive/2, check_negative/2, calc_hash/2]).
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check_positive(KeyCount, LoopCount) ->
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KeyList = produce_keylist(KeyCount),
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Bloom = leveled_rice:create_bloom(KeyList),
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check_positive(KeyList, Bloom, LoopCount).
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check_positive(_, Bloom, 0) ->
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{ok, byte_size(Bloom)};
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check_positive(KeyList, Bloom, LoopCount) ->
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true = leveled_rice:check_keys(KeyList, Bloom),
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check_positive(KeyList, Bloom, LoopCount - 1).
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produce_keylist(KeyCount) ->
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KeyPrefix = lists:concat(["PositiveKey-", random:uniform(KeyCount)]),
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produce_keylist(KeyCount, [], KeyPrefix).
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produce_keylist(0, KeyList, _) ->
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KeyList;
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produce_keylist(KeyCount, KeyList, KeyPrefix) ->
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Key = lists:concat([KeyPrefix, KeyCount]),
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produce_keylist(KeyCount - 1, [Key|KeyList], KeyPrefix).
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check_negative(KeyCount, CheckCount) ->
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KeyList = produce_keylist(KeyCount),
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Bloom = leveled_rice:create_bloom(KeyList),
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check_negative(Bloom, CheckCount, 0).
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check_negative(Bloom, 0, FalsePos) ->
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{byte_size(Bloom), FalsePos};
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check_negative(Bloom, CheckCount, FalsePos) ->
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Key = lists:concat(["NegativeKey-", CheckCount, random:uniform(CheckCount)]),
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case leveled_rice:check_key(Key, Bloom) of
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true -> check_negative(Bloom, CheckCount - 1, FalsePos + 1);
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false -> check_negative(Bloom, CheckCount - 1, FalsePos)
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end.
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calc_hash(_, 0) ->
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ok;
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calc_hash(Key, Count) ->
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erlang:phash2(lists:concat([Key, Count, "sometxt"])),
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calc_hash(Key, Count -1).
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