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74 lines
1.6 KiB
C++
74 lines
1.6 KiB
C++
// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
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#include "Luau/UnionFind.h"
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#include "Luau/Common.h"
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#include <limits>
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namespace Luau::EqSat
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{
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Id UnionFind::makeSet()
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{
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LUAU_ASSERT(parents.size() < std::numeric_limits<uint32_t>::max());
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Id id{uint32_t(parents.size())};
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parents.push_back(id);
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ranks.push_back(0);
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return id;
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}
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Id UnionFind::find(Id id) const
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{
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return canonicalize(id);
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}
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Id UnionFind::find(Id id)
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{
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Id set = canonicalize(id);
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// An e-class id 𝑎 is canonical iff find(𝑎) = 𝑎.
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while (id != parents[uint32_t(id)])
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{
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// Note: we don't update the ranks here since a rank
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// represents the upper bound on the maximum depth of a tree
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Id parent = parents[uint32_t(id)];
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parents[uint32_t(id)] = set;
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id = parent;
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}
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return set;
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}
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Id UnionFind::merge(Id a, Id b)
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{
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Id aSet = find(a);
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Id bSet = find(b);
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if (aSet == bSet)
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return aSet;
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// Ensure that the rank of set A is greater than the rank of set B
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if (ranks[uint32_t(aSet)] > ranks[uint32_t(bSet)])
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std::swap(aSet, bSet);
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parents[uint32_t(bSet)] = aSet;
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if (ranks[uint32_t(aSet)] == ranks[uint32_t(bSet)])
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ranks[uint32_t(aSet)]++;
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return aSet;
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}
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Id UnionFind::canonicalize(Id id) const
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{
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LUAU_ASSERT(uint32_t(id) < parents.size());
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// An e-class id 𝑎 is canonical iff find(𝑎) = 𝑎.
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while (id != parents[uint32_t(id)])
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id = parents[uint32_t(id)];
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return id;
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}
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} // namespace Luau::EqSat
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