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Merge from upstream

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This commit is contained in:
Akash Levy 2025-08-21 17:56:55 -07:00
commit e54fa487b8
29 changed files with 1314 additions and 793 deletions
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42
kernel/hashlib.h
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@ -12,6 +12,7 @@
#ifndef HASHLIB_H
#define HASHLIB_H
#include <array>
#include <stdexcept>
#include <algorithm>
#include <set>
@ -101,7 +102,7 @@ private:
uint32_t hash = ((a << 5) + a) ^ b;
return hash;
}
public:
public:
void hash32(uint32_t i) {
state = djb2_xor(i, state);
state = mkhash_xorshift(fudge ^ state);
@ -128,6 +129,7 @@ private:
*this = hash_ops<T>::hash_into(t, *this);
}
[[deprecated]]
void commutative_eat(hash_t t) {
state ^= t;
}
@ -357,6 +359,29 @@ template<typename K, int offset = 0, typename OPS = hash_ops<K>> class idict;
template<typename K, typename OPS = hash_ops<K>> class pool;
template<typename K, typename OPS = hash_ops<K>> class mfp;
// Computes the hash value of an unordered set of elements.
// See https://www.preprints.org/manuscript/201710.0192/v1/download.
// This is the Sum(4) algorithm from that paper, which has good collision resistance,
// much better than Sum(1) or Xor(1) (and somewhat better than Xor(4)).
class commutative_hash {
public:
commutative_hash() {
buckets.fill(0);
}
void eat(Hasher h) {
Hasher::hash_t v = h.yield();
size_t index = v & (buckets.size() - 1);
buckets[index] += v;
}
[[nodiscard]] Hasher hash_into(Hasher h) const {
for (auto b : buckets)
h.eat(b);
return h;
}
private:
std::array<Hasher::hash_t, 4> buckets;
};
template<typename K, typename T, typename OPS>
class dict {
struct entry_t
@ -802,14 +827,14 @@ public:
}
[[nodiscard]] Hasher hash_into(Hasher h) const {
commutative_hash comm;
for (auto &it : entries) {
Hasher entry_hash;
entry_hash.eat(it.udata.first);
entry_hash.eat(it.udata.second);
h.commutative_eat(entry_hash.yield());
comm.eat(entry_hash);
}
h.eat(entries.size());
return h;
return comm.hash_into(h);
}
void reserve(size_t n) { entries.reserve(n); }
@ -1190,11 +1215,11 @@ public:
}
[[nodiscard]] Hasher hash_into(Hasher h) const {
commutative_hash comm;
for (auto &it : entries) {
h.commutative_eat(ops.hash(it.udata).yield());
comm.eat(ops.hash(it.udata));
}
h.eat(entries.size());
return h;
return comm.hash_into(h);
}
void reserve(size_t n) { entries.reserve(n); }
@ -1359,7 +1384,8 @@ public:
return p;
}
// Merge sets if the given indices belong to different sets
// Merge sets if the given indices belong to different sets.
// Makes ifind(j) the root of the merged set.
void imerge(int i, int j)
{
i = ifind(i);