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Use bel for powers of two

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D’oh.  That’s much much faster of course!
This commit is contained in:
Martin Sumner 2017-01-24 18:09:51 +00:00
parent 8c3d0fc493
commit f8f2e02d92
1 changed files with 34 additions and 39 deletions
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73
src/leveled_tinybloom.erl
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@ -9,22 +9,6 @@
-include("include/leveled.hrl").
-define(TWO_POWER,
list_to_tuple(
lists:reverse(
element(2,
lists:foldl(
fun(_I, {AccLast, AccList}) ->
{AccLast * 2,
[(AccLast * 2)|AccList]}
end,
{1, [1]},
lists:seq(2, 32))
)
)
)
).
-include_lib("eunit/include/eunit.hrl").
-export([
@ -48,13 +32,9 @@ create_bloom(HashList) ->
0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0);
L when L > 16 ->
add_hashlist(HashList,
array:new([{size, 4}, {default, 0}]),
3);
add_hashlist(HashList, 3, 0, 0, 0, 0);
_ ->
add_hashlist(HashList,
array:new([{size, 2}, {default, 0}]),
1)
add_hashlist(HashList, 1, 0, 0)
end.
check_hash(_Hash, <<>>) ->
@ -87,23 +67,43 @@ split_hash(Hash, SlotSplit) ->
get_mask(H0, H1) ->
case H0 == H1 of
true ->
element(H0 + 1, ?TWO_POWER);
1 bsl H0;
false ->
element(H0 + 1, ?TWO_POWER) + element(H1 + 1, ?TWO_POWER)
(1 bsl H0) + (1 bsl H1)
end.
add_hashlist([], SlotArray, SlotSplit) ->
BuildBinFun =
fun(I, Acc) ->
Bloom = array:get(I, SlotArray),
<<Acc/binary, Bloom:32/integer>>
end,
lists:foldl(BuildBinFun, <<>>, lists:seq(0, SlotSplit));
add_hashlist([TopHash|T], SlotArray, SlotSplit) ->
%% This looks ugly and clunky, but in tests it was quicker than modifying an
%% Erlang term like an array as it is passed around the loop
add_hashlist([], _S, S0, S1) ->
<<S0:32/integer, S1:32/integer>>;
add_hashlist([TopHash|T], SlotSplit, S0, S1) ->
{Slot, H0, H1} = split_hash(TopHash, SlotSplit),
SW = os:timestamp(),
Mask = get_mask(H0, H1),
case Slot of
0 ->
add_hashlist(T, SlotSplit, S0 bor Mask, S1);
1 ->
add_hashlist(T, SlotSplit, S0, S1 bor Mask)
end.
add_hashlist([], _S, S0, S1, S2, S3) ->
<<S0:32/integer, S1:32/integer, S2:32/integer, S3:32/integer>>;
add_hashlist([TopHash|T], SlotSplit, S0, S1, S2, S3) ->
{Slot, H0, H1} = split_hash(TopHash, SlotSplit),
Mask = get_mask(H0, H1),
I = array:get(Slot, SlotArray),
add_hashlist(T, array:set(Slot, I bor Mask, SlotArray), SlotSplit).
case Slot of
0 ->
add_hashlist(T, SlotSplit, S0 bor Mask, S1, S2, S3);
1 ->
add_hashlist(T, SlotSplit, S0, S1 bor Mask, S2, S3);
2 ->
add_hashlist(T, SlotSplit, S0, S1, S2 bor Mask, S3);
3 ->
add_hashlist(T, SlotSplit, S0, S1, S2, S3 bor Mask)
end.
add_hashlist([], _S, S0, S1, S2, S3, S4, S5, S6, S7, S8, S9,
SA, SB, SC, SD, SE, SF) ->
@ -330,11 +330,6 @@ test_bloom(N) ->
++ " build ~w check ~w neg_check ~w and fpr ~w~n",
[N, TSa, TSb, TSc, FPR]).
twopower_test() ->
?assertMatch(1, element(1, ?TWO_POWER)),
?assertMatch(128, element(8, ?TWO_POWER)),
?assertMatch(2147483648, element(32, ?TWO_POWER)).
-endif.