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Lightweight int3 hash function

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This commit is contained in:
Tomasz Zieliński
2023-12-18 13:55:54 +01:00
parent c701d42781
commit 038bcd32f6
1 changed files with 16 additions and 8 deletions
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22
lib/int3.h
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@@ -180,6 +180,19 @@ public:
return { { int3(0,1,0),int3(0,-1,0),int3(-1,0,0),int3(+1,0,0), return { { int3(0,1,0),int3(0,-1,0),int3(-1,0,0),int3(+1,0,0),
int3(1,1,0),int3(-1,1,0),int3(1,-1,0),int3(-1,-1,0) } }; int3(1,1,0),int3(-1,1,0),int3(1,-1,0),int3(-1,-1,0) } };
} }
// Solution by ChatGPT
// Assume values up to +- 1000
friend std::size_t hash_value(const int3& v) {
// Since the range is [-1000, 1000], offsetting by 1000 maps it to [0, 2000]
std::size_t hx = v.x + 1000;
std::size_t hy = v.y + 1000;
std::size_t hz = v.z + 1000;
// Combine the hash values, multiplying them by prime numbers
return (hx * 4000037u) ^ (hy * 2003u) + hz;
}
}; };
template<typename Container> template<typename Container>
@@ -204,14 +217,9 @@ int3 findClosestTile (Container & container, int3 dest)
VCMI_LIB_NAMESPACE_END VCMI_LIB_NAMESPACE_END
template<> template<>
struct std::hash<VCMI_LIB_WRAP_NAMESPACE(int3)> { struct std::hash<VCMI_LIB_WRAP_NAMESPACE(int3)> {
size_t operator()(VCMI_LIB_WRAP_NAMESPACE(int3) const& pos) const std::size_t operator()(VCMI_LIB_WRAP_NAMESPACE(int3) const& pos) const noexcept {
{ return hash_value(pos);
size_t ret = std::hash<int>()(pos.x);
VCMI_LIB_WRAP_NAMESPACE(vstd)::hash_combine(ret, pos.y);
VCMI_LIB_WRAP_NAMESPACE(vstd)::hash_combine(ret, pos.z);
return ret;
} }
}; };