Initial Commit for SkipLists
To speed check on alternate platform
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martinsumner
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e06888ad58
commit
96b9e1faa3
1 changed files with 136 additions and 1 deletions
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@ -52,6 +52,7 @@
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-include_lib("eunit/include/eunit.hrl").
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-define(SLOT_WIDTH, {4096, 12}).
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-define(SKIP_WIDTH, 128).
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%%%============================================================================
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@ -146,6 +147,72 @@ merge_trees(StartKey, EndKey, TreeList, LevelMinus1) ->
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gb_trees:empty(),
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lists:append(TreeList, [LevelMinus1])).
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%%%============================================================================
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%%% SkipList
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%%%============================================================================
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generate_skiplist(Dict) ->
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KVL = lists:ukeysort(1, dict:to_list(Dict)),
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Slots = length(KVL) div ?SKIP_WIDTH,
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SkipList0 = lists:map(fun(X) ->
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N = X * ?SKIP_WIDTH,
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{K, _V} = lists:nth(N, KVL),
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{K, lists:sublist(KVL,
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N - ?SKIP_WIDTH + 1,
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?SKIP_WIDTH)}
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end,
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lists:seq(1, length(KVL) div ?SKIP_WIDTH)),
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case Slots * ?SKIP_WIDTH < length(KVL) of
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true ->
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{LastK, _V} = lists:last(KVL),
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SkipList0 ++ [{LastK, lists:nthtail(Slots * ?SKIP_WIDTH, KVL)}];
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false ->
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SkipList0
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end.
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fetchkey_from_skiplist(SkipList, Key) ->
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SubList = lists:foldl(fun({SkipKey, SL}, Acc) ->
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case {Acc, SkipKey} of
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{null, SkipKey} when SkipKey >= Key ->
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SL;
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_ ->
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Acc
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end end,
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null,
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SkipList),
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case SubList of
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null ->
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not_found;
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SubList ->
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case lists:keyfind(Key, 1, SubList) of
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false ->
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not_found;
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{Key, V} ->
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{Key, V}
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end
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end.
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fetchrange_from_skiplist(SkipList, StartKey, EndKey) ->
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R = lists:foldl(fun({SkipKey, SL}, {Continue, Acc}) ->
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case Continue of
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true ->
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case SkipKey of
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SkipKey when StartKey >= SkipKey ->
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{true, Acc};
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SkipKey when EndKey < SkipKey ->
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{false, Acc ++ SL}
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end;
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false ->
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{false, Acc}
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end end,
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{true, []},
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SkipList),
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{_Bool, SubList} = R,
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SubList.
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%%%============================================================================
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%%% Internal Functions
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%%%============================================================================
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@ -277,6 +344,74 @@ compare_method_test() ->
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[timer:now_diff(os:timestamp(), SWb), Sz1]),
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?assertMatch(Sz0, Sz1).
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skiplist_test() ->
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KL = gb_trees:to_list(generate_randomkeys(1, 4000, 1, 200)),
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D = lists:foldl(fun({K, V}, Acc) -> dict:store(K, V, Acc) end,
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dict:new(),
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KL),
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SWa = os:timestamp(),
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SkipList = generate_skiplist(D),
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io:format("Generating skip list with 4000 keys in ~w microseconds~n",
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[timer:now_diff(os:timestamp(), SWa)]),
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CheckList1 = lists:sublist(KL, 1200, 100),
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CheckList2 = lists:sublist(KL, 1600, 100),
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CheckList3 = lists:sublist(KL, 2000, 100),
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CheckList4 = lists:sublist(KL, 2400, 100),
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CheckList5 = lists:sublist(KL, 2800, 100),
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CheckList6 = lists:sublist(KL, 1, 10),
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CheckList7 = lists:nthtail(3800, KL),
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CheckAll = CheckList1 ++ CheckList2 ++ CheckList3 ++
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CheckList4 ++ CheckList5 ++ CheckList6 ++ CheckList7,
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SWb = os:timestamp(),
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lists:foreach(fun({K, V}) ->
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?assertMatch({K, V},
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fetchkey_from_skiplist(SkipList, K))
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end,
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CheckAll),
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io:format("Finding 520 keys took ~w microseconds~n",
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[timer:now_diff(os:timestamp(), SWb)]),
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SWc = os:timestamp(),
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KR1 = fetchrange_from_skiplist(SkipList,
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lists:nth(1, CheckList1),
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lists:last(CheckList1)),
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?assertMatch(true, length(KR1) >= 100),
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?assertMatch(true, length(KR1) < 400),
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KR2 = fetchrange_from_skiplist(SkipList,
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lists:nth(1, CheckList2),
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lists:last(CheckList2)),
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?assertMatch(true, length(KR2) >= 100),
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?assertMatch(true, length(KR2) < 400),
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KR3 = fetchrange_from_skiplist(SkipList,
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lists:nth(1, CheckList3),
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lists:last(CheckList3)),
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?assertMatch(true, length(KR3) >= 100),
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?assertMatch(true, length(KR3) < 400),
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KR4 = fetchrange_from_skiplist(SkipList,
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lists:nth(1, CheckList4),
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lists:last(CheckList4)),
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?assertMatch(true, length(KR4) >= 100),
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?assertMatch(true, length(KR4) < 400),
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KR5 = fetchrange_from_skiplist(SkipList,
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lists:nth(1, CheckList5),
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lists:last(CheckList5)),
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?assertMatch(true, length(KR5) >= 100),
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?assertMatch(true, length(KR5) < 400),
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KR6 = fetchrange_from_skiplist(SkipList,
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lists:nth(1, CheckList6),
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lists:last(CheckList6)),
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?assertMatch(true, length(KR6) >= 10),
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?assertMatch(true, length(KR6) < 200),
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KR7 = fetchrange_from_skiplist(SkipList,
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lists:nth(1, CheckList7),
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lists:last(CheckList7)),
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?assertMatch(true, length(KR7) >= 10),
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?assertMatch(true, length(KR7) < 200),
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io:format("Finding 7 ranges took ~w microseconds~n",
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[timer:now_diff(os:timestamp(), SWc)]),
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?assertMatch(true, false).
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-endif.
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