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optimize unionfind

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birds3345 2024-07-17 01:21:07 -04:00
parent 4f917420d7
commit 06c99b75de
2 changed files with 29 additions and 0 deletions
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2
EqSat/include/Luau/UnionFind.h
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@ -13,10 +13,12 @@ struct UnionFind final
{ {
Id makeSet(); Id makeSet();
Id find(Id id) const; Id find(Id id) const;
Id find(Id id);
void merge(Id a, Id b); void merge(Id a, Id b);
private: private:
std::vector<Id> parents; std::vector<Id> parents;
std::vector<unsigned int> ranks;
}; };
} // namespace Luau::EqSat } // namespace Luau::EqSat

27
EqSat/src/UnionFind.cpp
View file

@ -10,6 +10,8 @@ Id UnionFind::makeSet()
{ {
Id id{parents.size()}; Id id{parents.size()};
parents.push_back(id); parents.push_back(id);
ranks.push_back(0);
return id; return id;
} }
@ -24,12 +26,37 @@ Id UnionFind::find(Id id) const
return id; return id;
} }
Id UnionFind::find(Id id)
{
LUAU_ASSERT(size_t(id) < parents.size());
// An e-class id 𝑎 is canonical iff find(𝑎) = 𝑎.
if (id != parents[size_t(id)])
// Note: we don't update the ranks here since a rank
// represents the upper bound on the maximum depth of a tree
parents[size_t(id)] = find(parents[size_t(id)]);
return parents[size_t(id)];
}
void UnionFind::merge(Id a, Id b) void UnionFind::merge(Id a, Id b)
{ {
LUAU_ASSERT(size_t(a) < parents.size()); LUAU_ASSERT(size_t(a) < parents.size());
LUAU_ASSERT(size_t(b) < parents.size()); LUAU_ASSERT(size_t(b) < parents.size());
Id aSet = find(a);
Id bSet = find(b);
if (aSet == bSet)
return;
// Ensure that the rank of set A is greater than the rank of set B
if (ranks[size_t(aSet)] < ranks[size_t(bSet)])
std::swap(a, b);
parents[size_t(b)] = a; parents[size_t(b)] = a;
if (ranks[size_t(aSet)] == ranks[size_t(bSet)])
ranks[size_t(aSet)]++;
} }
} // namespace Luau::EqSat } // namespace Luau::EqSat