diff options
| -rw-r--r-- | erts/emulator/test/nif_SUITE.erl | 42 |
1 files changed, 25 insertions, 17 deletions
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl index f9ee96c9ca..bcea9e3539 100644 --- a/erts/emulator/test/nif_SUITE.erl +++ b/erts/emulator/test/nif_SUITE.erl @@ -2637,9 +2637,9 @@ nif_snprintf(Config) -> nif_internal_hash(Config) -> ensure_lib_loaded(Config), HashValueBitSize = nif_hash_result_bitsize(internal), - Terms = unique([random_term() || _ <- lists:seq(1, 5000)]), + Terms = unique([random_term() || _ <- lists:seq(1, 500)]), HashValues = [hash_nif(internal, Term, 0) || Term <- Terms], - test_bit_distribution_fitness(HashValues, HashValueBitSize, 0.05). + test_bit_distribution_fitness(HashValues, HashValueBitSize). nif_internal_hash_salted(Config) -> ensure_lib_loaded(Config), @@ -2648,7 +2648,7 @@ nif_internal_hash_salted(Config) -> nif_phash2(Config) -> ensure_lib_loaded(Config), HashValueBitSize = nif_hash_result_bitsize(phash2), - Terms = unique([random_term() || _ <- lists:seq(1, 5000)]), + Terms = unique([random_term() || _ <- lists:seq(1, 500)]), HashValues = lists:map( fun (Term) -> @@ -2661,12 +2661,12 @@ nif_phash2(Config) -> HashValue end, Terms), - test_bit_distribution_fitness(HashValues, HashValueBitSize, 0.05). + test_bit_distribution_fitness(HashValues, HashValueBitSize). test_salted_nif_hash(HashType) -> HashValueBitSize = nif_hash_result_bitsize(HashType), - Terms = unique([random_term() || _ <- lists:seq(1, 5000)]), - Salts = unique([random_uint32() || _ <- lists:seq(1, 100)]), + Terms = unique([random_term() || _ <- lists:seq(1, 500)]), + Salts = unique([random_uint32() || _ <- lists:seq(1, 50)]), {HashValuesPerSalt, HashValuesPerTerm} = lists:mapfoldl( fun (Salt, Acc) -> @@ -2687,22 +2687,20 @@ test_salted_nif_hash(HashType) -> % Test per-salt hash distribution of different terms lists:foreach( fun ({_Salt, HashValues}) -> - test_bit_distribution_fitness(HashValues, HashValueBitSize, 0.05) + test_bit_distribution_fitness(HashValues, HashValueBitSize) end, HashValuesPerSalt), % Test per-term hash distribution of different salts dict:fold( fun (_Term, HashValues, Acc) -> - % Be more tolerant of relative deviation, - % as there's fewer hash values here. - test_bit_distribution_fitness(HashValues, HashValueBitSize, 0.30), + test_bit_distribution_fitness(HashValues, HashValueBitSize), Acc end, ok, HashValuesPerTerm). -test_bit_distribution_fitness(Integers, BitSize, MaxRelativeDeviation) -> +test_bit_distribution_fitness(Integers, BitSize) -> MaxInteger = (1 bsl BitSize) - 1, OnesPerBit = lists:foldl( @@ -2718,19 +2716,29 @@ test_bit_distribution_fitness(Integers, BitSize, MaxRelativeDeviation) -> orddict:new(), Integers), - ExpectedNrOfOnes = length(Integers) div 2, + N = length(Integers), + ExpectedNrOfOnes = N div 2, + %% ExpectedNrOfOnes should have a binomial distribution + %% with a standard deviation as: + ExpectedStdDev = math:sqrt(N) / 2, + %% which can be approximated as a normal distribution + %% where we allow a deviation of 6 std.devs + %% for a fail probability of 0.000000002: + MaxStdDevs = 6, + FailureText = orddict:fold( fun (BitIndex, NrOfOnes, Acc) -> - RelativeDeviation = abs(NrOfOnes - ExpectedNrOfOnes) / length(Integers), - case RelativeDeviation >= MaxRelativeDeviation of - false -> Acc; + Deviation = abs(NrOfOnes - ExpectedNrOfOnes) / ExpectedStdDev, + case Deviation >= MaxStdDevs of + false -> + Acc; true -> [Acc, io_lib:format( "Unreasonable deviation on number of set bits (i=~p): " - "expected ~p, got ~p (relative dev. ~.3f)~n", - [BitIndex, ExpectedNrOfOnes, NrOfOnes, RelativeDeviation])] + "expected ~p, got ~p (# std.dev ~.3f > ~p)~n", + [BitIndex, ExpectedNrOfOnes, NrOfOnes, Deviation, MaxStdDevs])] end end, [], |