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authorGuilherme Andrade <[email protected]>2017-04-22 18:40:26 +0100
committerGuilherme Andrade <[email protected]>2017-04-22 18:40:26 +0100
commitc94506ccc003016db49fa2dbe5741196e071d45a (patch)
tree6a2735542606a7b33298d8455cd9f17f9a164be8 /erts
parent21e1d879faaae2278a68200fe1085d7e73791fa0 (diff)
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erts: Add test cases for salted enif_hash calls
Diffstat (limited to 'erts')
-rw-r--r--erts/emulator/test/nif_SUITE.erl148
1 files changed, 107 insertions, 41 deletions
diff --git a/erts/emulator/test/nif_SUITE.erl b/erts/emulator/test/nif_SUITE.erl
index 36af68be60..6e4866bfd8 100644
--- a/erts/emulator/test/nif_SUITE.erl
+++ b/erts/emulator/test/nif_SUITE.erl
@@ -58,7 +58,9 @@
nif_port_command/1,
nif_snprintf/1,
nif_internal_hash/1,
- nif_phash2/1
+ nif_internal_hash_salted/1,
+ nif_phash2/1,
+ nif_phash2_salted/1
]).
-export([many_args_100/100]).
@@ -94,7 +96,9 @@ all() ->
nif_port_command,
nif_snprintf,
nif_internal_hash,
- nif_phash2].
+ nif_internal_hash_salted,
+ nif_phash2,
+ nif_phash2_salted].
groups() ->
[{G, [], api_repeaters()} || G <- api_groups()]
@@ -2616,57 +2620,119 @@ nif_snprintf(Config) ->
nif_internal_hash(Config) ->
ensure_lib_loaded(Config),
- Terms =
- [random_term() || _ <- lists:seq(1, 5000)],
+ HashValueBitSize = nif_hash_result_bitsize(internal),
+ Terms = unique([random_term() || _ <- lists:seq(1, 5000)]),
+ HashValues = [hash_nif(internal, Term, 0) || Term <- Terms],
+ test_bit_distribution_fitness(HashValues, HashValueBitSize, 0.05).
- % Unlike the phash2 hash, in this case we
- % have nothing to compare to, so let's try
- % and at least make sure the distribution
- % isn't outright wrong, statistical nuances
- % aside.
+nif_internal_hash_salted(Config) ->
+ ensure_lib_loaded(Config),
+ test_salted_nif_hash(internal).
+
+nif_phash2(Config) ->
+ ensure_lib_loaded(Config),
+ HashValueBitSize = nif_hash_result_bitsize(phash2),
+ Terms = unique([random_term() || _ <- lists:seq(1, 5000)]),
+ HashValues =
+ lists:map(
+ fun (Term) ->
+ HashValue = erlang:phash2(Term),
+ NifHashValue = hash_nif(phash2, Term, 0),
+ (HashValue =:= NifHashValue
+ orelse ct:fail("Expected: ~p\nActual: ~p",
+ [HashValue, NifHashValue])),
+ HashValue
+ end,
+ Terms),
+ test_bit_distribution_fitness(HashValues, HashValueBitSize, 0.05).
+
+nif_phash2_salted(Config) ->
+ ensure_lib_loaded(Config),
+ test_salted_nif_hash(phash2).
+
+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)]),
+ {HashValuesPerSalt, HashValuesPerTerm} =
+ lists:mapfoldl(
+ fun (Salt, Acc) ->
+ {HashValues, NewAcc} =
+ lists:mapfoldl(
+ fun (Term, AccB) ->
+ HashValue = hash_nif(HashType, Term, Salt),
+ NewAccB = dict:append(Term, HashValue, AccB),
+ {HashValue, NewAccB}
+ end,
+ Acc,
+ Terms),
+ {{Salt, HashValues}, NewAcc}
+ end,
+ dict:new(),
+ Salts),
+
+ % Test per-salt hash distribution of different terms
+ lists:foreach(
+ fun ({_Salt, HashValues}) ->
+ test_bit_distribution_fitness(HashValues, HashValueBitSize, 0.05)
+ 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),
+ Acc
+ end,
+ ok,
+ HashValuesPerTerm).
+
+test_bit_distribution_fitness(Integers, BitSize, MaxRelativeDeviation) ->
+ MaxInteger = (1 bsl BitSize) - 1,
OnesPerBit =
lists:foldl(
- fun (Term, Acc) ->
- NifHashValue = hash_nif(internal, Term, 0),
+ fun (Integer, Acc) when Integer >= 0, Integer =< MaxInteger ->
lists:foldl(
fun (BitIndex, AccB) ->
- BitValue = (NifHashValue band (1 bsl BitIndex)) bsr BitIndex,
- dict:update_counter(BitIndex, BitValue, AccB)
+ BitValue = (Integer band (1 bsl BitIndex)) bsr BitIndex,
+ orddict:update_counter(BitIndex, BitValue, AccB)
end,
Acc,
- lists:seq(0, 31))
+ lists:seq(0, BitSize - 1))
end,
- dict:new(),
- Terms),
+ orddict:new(),
+ Integers),
+
+ ExpectedNrOfOnes = length(Integers) div 2,
+ FailureText =
+ orddict:fold(
+ fun (BitIndex, NrOfOnes, Acc) ->
+ RelativeDeviation = abs(NrOfOnes - ExpectedNrOfOnes) / length(Integers),
+ case RelativeDeviation >= MaxRelativeDeviation 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])]
+ end
+ end,
+ [],
+ OnesPerBit),
- ExpectedNrOfOnes = length(Terms) div 2,
- dict:fold(
- fun (BitIndex, NrOfOnes, Acc) ->
- RelativeDeviation = abs(NrOfOnes - ExpectedNrOfOnes) / ExpectedNrOfOnes,
- (RelativeDeviation < 0.10
- orelse ct:fail("Unreasonable deviation on number of set bits (i=~p): "
- "expected ~p, got ~p (relative dev. ~.3f)",
- [BitIndex, ExpectedNrOfOnes, NrOfOnes, RelativeDeviation])),
- Acc
- end,
- ok,
- OnesPerBit).
+ (FailureText =:= [] orelse ct:fail(FailureText)).
-nif_phash2(Config) ->
- ensure_lib_loaded(Config),
- Terms =
- [random_term() || _ <- lists:seq(1, 5000)],
+nif_hash_result_bitsize(internal) -> 32;
+nif_hash_result_bitsize(phash2) -> 27.
- lists:foreach(
- fun (Term) ->
- HashValue = erlang:phash2(Term),
- NifHashValue = hash_nif(phash2, Term, 0),
- (HashValue =:= NifHashValue
- orelse ct:fail("Expected: ~p\nActual: ~p",
- [HashValue, NifHashValue]))
- end,
- Terms).
+unique(List) ->
+ lists:usort(List).
+
+random_uint32() ->
+ rand:uniform(1 bsl 32) - 1.
random_term() ->
case rand:uniform(6) of