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authorMikhail Yashkov <[email protected]>2016-10-23 17:52:07 +0300
committerMikhail Yashkov <[email protected]>2016-11-08 17:58:17 +0300
commitcc939d5efc19484ba09a4fdcd8c70e9718026592 (patch)
treeeee2075ec631ddf473f8447cfb1b4f2d55c2544b /lib/stdlib
parentb36d72178ed0739d6bf71a8047ae0a026ceb4a64 (diff)
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Speed up sets:add_element/2 and sets:del_element/2
Optimize sets:add_element/2 when adding an element that is already present, and sets:del_element/2 when the element to be deleted is not present. This optimization can make certain operations, such as sets:union/2 with many overlapping elements, up to two orders of magnitude faster.
Diffstat (limited to 'lib/stdlib')
-rw-r--r--lib/stdlib/src/sets.erl66
1 files changed, 33 insertions, 33 deletions
diff --git a/lib/stdlib/src/sets.erl b/lib/stdlib/src/sets.erl
index 3e70450320..c65a13b22e 100644
--- a/lib/stdlib/src/sets.erl
+++ b/lib/stdlib/src/sets.erl
@@ -128,14 +128,14 @@ is_element(E, S) ->
Set2 :: set(Element).
add_element(E, S0) ->
Slot = get_slot(S0, E),
- {S1,Ic} = on_bucket(fun (B0) -> add_bkt_el(E, B0, B0) end, S0, Slot),
- maybe_expand(S1, Ic).
-
--spec add_bkt_el(T, [T], [T]) -> {[T], 0 | 1}.
-add_bkt_el(E, [E|_], Bkt) -> {Bkt,0};
-add_bkt_el(E, [_|B], Bkt) ->
- add_bkt_el(E, B, Bkt);
-add_bkt_el(E, [], Bkt) -> {[E|Bkt],1}.
+ Bkt = get_bucket(S0, Slot),
+ case lists:member(E, Bkt) of
+ true ->
+ S0;
+ false ->
+ S1 = update_bucket(S0, Slot, [E | Bkt]),
+ maybe_expand(S1)
+ end.
%% del_element(Element, Set) -> Set.
%% Return Set but with Element removed.
@@ -144,15 +144,28 @@ add_bkt_el(E, [], Bkt) -> {[E|Bkt],1}.
Set2 :: set(Element).
del_element(E, S0) ->
Slot = get_slot(S0, E),
- {S1,Dc} = on_bucket(fun (B0) -> del_bkt_el(E, B0) end, S0, Slot),
- maybe_contract(S1, Dc).
+ Bkt = get_bucket(S0, Slot),
+ case lists:member(E, Bkt) of
+ false ->
+ S0;
+ true ->
+ S1 = update_bucket(S0, Slot, lists:delete(E, Bkt)),
+ maybe_contract(S1, 1)
+ end.
--spec del_bkt_el(T, [T]) -> {[T], 0 | 1}.
-del_bkt_el(E, [E|Bkt]) -> {Bkt,1};
-del_bkt_el(E, [Other|Bkt0]) ->
- {Bkt1,Dc} = del_bkt_el(E, Bkt0),
- {[Other|Bkt1],Dc};
-del_bkt_el(_, []) -> {[],0}.
+%% update_bucket(Set, Slot, NewBucket) -> UpdatedSet.
+%% Replace bucket in Slot by NewBucket
+-spec update_bucket(Set1, Slot, Bkt) -> Set2 when
+ Set1 :: set(Element),
+ Set2 :: set(Element),
+ Slot :: non_neg_integer(),
+ Bkt :: [Element].
+update_bucket(Set, Slot, NewBucket) ->
+ SegI = ((Slot-1) div ?seg_size) + 1,
+ BktI = ((Slot-1) rem ?seg_size) + 1,
+ Segs = Set#set.segs,
+ Seg = element(SegI, Segs),
+ Set#set{segs = setelement(SegI, Segs, setelement(BktI, Seg, NewBucket))}.
%% union(Set1, Set2) -> Set
%% Return the union of Set1 and Set2.
@@ -272,19 +285,6 @@ get_slot(T, Key) ->
-spec get_bucket(set(), non_neg_integer()) -> term().
get_bucket(T, Slot) -> get_bucket_s(T#set.segs, Slot).
-%% on_bucket(Fun, Hashdb, Slot) -> {NewHashDb,Result}.
-%% Apply Fun to the bucket in Slot and replace the returned bucket.
--spec on_bucket(fun((_) -> {[_], 0 | 1}), set(E), non_neg_integer()) ->
- {set(E), 0 | 1}.
-on_bucket(F, T, Slot) ->
- SegI = ((Slot-1) div ?seg_size) + 1,
- BktI = ((Slot-1) rem ?seg_size) + 1,
- Segs = T#set.segs,
- Seg = element(SegI, Segs),
- B0 = element(BktI, Seg),
- {B1, Res} = F(B0), %Op on the bucket.
- {T#set{segs = setelement(SegI, Segs, setelement(BktI, Seg, B1))},Res}.
-
%% fold_set(Fun, Acc, Dictionary) -> Dictionary.
%% filter_set(Fun, Dictionary) -> Dictionary.
@@ -349,8 +349,8 @@ put_bucket_s(Segs, Slot, Bkt) ->
Seg = setelement(BktI, element(SegI, Segs), Bkt),
setelement(SegI, Segs, Seg).
--spec maybe_expand(set(E), 0 | 1) -> set(E).
-maybe_expand(T0, Ic) when T0#set.size + Ic > T0#set.exp_size ->
+-spec maybe_expand(set(E)) -> set(E).
+maybe_expand(T0) when T0#set.size + 1 > T0#set.exp_size ->
T = maybe_expand_segs(T0), %Do we need more segments.
N = T#set.n + 1, %Next slot to expand into
Segs0 = T#set.segs,
@@ -360,12 +360,12 @@ maybe_expand(T0, Ic) when T0#set.size + Ic > T0#set.exp_size ->
{B1,B2} = rehash(B, Slot1, Slot2, T#set.maxn),
Segs1 = put_bucket_s(Segs0, Slot1, B1),
Segs2 = put_bucket_s(Segs1, Slot2, B2),
- T#set{size = T#set.size + Ic,
+ T#set{size = T#set.size + 1,
n = N,
exp_size = N * ?expand_load,
con_size = N * ?contract_load,
segs = Segs2};
-maybe_expand(T, Ic) -> T#set{size = T#set.size + Ic}.
+maybe_expand(T) -> T#set{size = T#set.size + 1}.
-spec maybe_expand_segs(set(E)) -> set(E).
maybe_expand_segs(T) when T#set.n =:= T#set.maxn ->