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Greatly speed up sorted changeset calculations

This commit is contained in:
Thomas Goyne 2016-03-16 10:34:16 -07:00 committed by Thomas Goyne
parent 88a3b6ed00
commit 5d5f504543
1 changed files with 18 additions and 8 deletions
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26
src/collection_notifications.cpp
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@ -420,13 +420,24 @@ private:
Match find_longest_match(size_t begin1, size_t end1, size_t begin2, size_t end2)
{
struct Length {
size_t j, len;
};
std::vector<Length> cur;
std::vector<Length> prev;
auto length = [&](size_t j) -> size_t {
for (auto const& pair : prev) {
if (pair.j + 1 == j)
return pair.len + 1;
}
return 1;
};
Match best = {begin1, begin2, 0, 0};
std::vector<size_t> len_from_j;
len_from_j.resize(end2 - begin2, 0);
std::vector<size_t> len_from_j_prev = len_from_j;
for (size_t i = begin1; i < end1; ++i) {
std::fill(begin(len_from_j), end(len_from_j), 0);
cur.clear();
size_t ai = a[i].row_index;
auto it = lower_bound(begin(b), end(b), Row{ai, 0},
@ -438,9 +449,8 @@ private:
if (j >= end2)
break;
size_t off = j - begin2;
size_t size = off == 0 ? 1 : len_from_j_prev[off - 1] + 1;
len_from_j[off] = size;
size_t size = length(j);
cur.push_back({j, size});
if (size > best.size)
best = {i - size + 1, j - size + 1, size, npos};
// Given two equal-length matches, prefer the one with fewer modified rows
@ -454,7 +464,7 @@ private:
REALM_ASSERT(best.i >= begin1 && best.i + best.size <= end1);
REALM_ASSERT(best.j >= begin2 && best.j + best.size <= end2);
}
len_from_j.swap(len_from_j_prev);
cur.swap(prev);
}
return best;
}