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-rw-r--r--erts/emulator/test/nif_SUITE.erl42
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,
[],