Add membership timing tests - sets vs lists

test/member_test.erl

@@ -0,0 +1,51 @@
+-module(member_test).
+
+-export([test_membership/0]).
+
+-define(SEGMENTS_TO_CHECK, 32768). % a whole SST file
+-define(MEMBERSHIP_LENGTHS, [8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096]).
+
+segments(Length) ->
+    AllSegs = lists:seq(1, ?SEGMENTS_TO_CHECK),
+    AllSegsBin = 
+        lists:foldl(fun(I, Acc) -> <<Acc/binary, (I - 1):16/integer>> end, 
+                        <<>>,
+                        AllSegs),
+    StartPos = random:uniform(length(AllSegs) - Length),
+    {<<AllSegsBin/binary, AllSegsBin/binary, 
+            AllSegsBin/binary, AllSegsBin/binary>>,
+        lists:sublist(AllSegs, StartPos, Length)}.
+
+test_membership(Length) ->
+    {AllSegsBin, TestList} = segments(Length),
+    ExpectedOutput = 
+        lists:reverse(TestList ++ TestList ++ TestList ++ TestList),
+
+    SW0 = os:timestamp(),
+    TestListFun = fun(I) -> lists:member(I, TestList) end,
+    true = test_binary(AllSegsBin, [], TestListFun) == ExpectedOutput,
+    ListT = timer:now_diff(os:timestamp(), SW0) / 131072,
+
+    SW1 = os:timestamp(),
+    TestSet = sets:from_list(TestList),
+    TestSetsFun = fun(I) -> sets:is_element(I, TestSet) end,
+    true = test_binary(AllSegsBin, [], TestSetsFun) == ExpectedOutput,
+    SetsT = timer:now_diff(os:timestamp(), SW1) / 131072,
+
+    io:format("Test with segment count ~w  ..."
+                ++ " took ~w ms per 1000 checks with list ..." 
+                ++ " took ~w ms per 1000 checks with set~n", [Length, ListT, SetsT]).
+
+
+test_binary(<<>>, Acc, _TestFun) ->
+    Acc;
+test_binary(<<0:1/integer, TestSeg:15/integer, Rest/binary>>, Acc, TestFun) ->
+    case TestFun(TestSeg) of
+        true ->
+            test_binary(Rest, [TestSeg|Acc], TestFun);
+        false ->
+            test_binary(Rest, Acc, TestFun)
+    end.
+
+test_membership() ->
+    lists:foreach(fun(I) -> test_membership(I) end, ?MEMBERSHIP_LENGTHS).