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Improve from_list in skiplist

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form_list had taken a suprrising amount of time - so improved the
efficiency of this
This commit is contained in:
martinsumner 2017-01-05 13:57:38 +00:00
parent c43014a0ee
commit 34a25bdb88
1 changed files with 21 additions and 47 deletions
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66
src/leveled_skiplist.erl
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@ -188,53 +188,27 @@ enter(Key, Value, Hash, SkipList, Width, Level) ->
{MarkerKey, UpdSubSkipList})
end.
from_list(SkipList, _SkipWidth, 0) ->
SkipList;
from_list(KVList, SkipWidth, ListHeight) ->
L0 = length(KVList),
SL0 =
case L0 > SkipWidth of
true ->
from_list(KVList, L0, [], SkipWidth);
false ->
{LastK, _LastSL} = lists:last(KVList),
[{LastK, KVList}]
end,
from_list(SL0, SkipWidth, ListHeight - 1).
from_list(KVL, Width, 1) ->
Slots = length(KVL) div Width,
SkipList0 = lists:map(fun(X) ->
N = X * Width,
{K, _V} = lists:nth(N, KVL),
{K, lists:sublist(KVL,
N - Width + 1,
Width)}
end,
lists:seq(1, length(KVL) div Width)),
case Slots * Width < length(KVL) of
true ->
{LastK, _V} = lists:last(KVL),
SkipList0 ++ [{LastK, lists:nthtail(Slots * Width, KVL)}];
false ->
SkipList0
end;
from_list(KVL, Width, Level) ->
SkipWidth = width(Level, Width),
LoftSlots = length(KVL) div SkipWidth,
case LoftSlots of
0 ->
{K, _V} = lists:last(KVL),
[{K, from_list(KVL, Width, Level - 1)}];
_ ->
SkipList0 =
lists:map(fun(X) ->
N = X * SkipWidth,
{K, _V} = lists:nth(N, KVL),
SL = lists:sublist(KVL,
N - SkipWidth + 1,
SkipWidth),
{K, from_list(SL, Width, Level - 1)}
end,
lists:seq(1, LoftSlots)),
case LoftSlots * SkipWidth < length(KVL) of
true ->
{LastK, _V} = lists:last(KVL),
TailList = lists:nthtail(LoftSlots * SkipWidth, KVL),
SkipList0 ++ [{LastK, from_list(TailList,
Width,
Level - 1)}];
false ->
SkipList0
end
end.
from_list([], 0, SkipList, SkipWidth) ->
SkipList;
from_list(KVList, L, SkipList, SkipWidth) ->
SubLL = min(SkipWidth, L),
{Head, Tail} = lists:split(SubLL, KVList),
{LastK, _LastV} = lists:last(Head),
from_list(Tail, L - SubLL, SkipList ++ [{LastK, Head}], SkipWidth).
list_lookup(Key, SkipList, 1) ->