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fix: replace O(n²) path dedup with O(1) hash set lookup #7070

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fix: replace O(n²) path dedup with O(1) hash set lookup #7070

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f4e1dc7
fix: replace O(n²) path dedup with O(1) hash set lookup
dangell7 May 4, 2026
8132727
Merge branch 'develop' into dangell7/fix-pathfinder-dedup
dangell7 May 5, 2026
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6 changes: 6 additions & 0 deletions include/xrpl/protocol/STPathSet.h
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Original file line number Diff line number Diff line change
Expand Up @@ -111,6 +111,12 @@ class STPathElement final : public CountedObject<STPathElement>
bool
operator!=(STPathElement const& t) const;

[[nodiscard]] std::size_t
hash() const noexcept
{
return hash_value_;
}
Comment on lines +114 to +118

private:
static std::size_t
getHash(STPathElement const& element);
Expand Down
22 changes: 9 additions & 13 deletions src/xrpld/rpc/detail/Pathfinder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@
#include <optional>
#include <ostream>
#include <string>
#include <unordered_set>
#include <vector>

namespace xrpl {
Expand Down Expand Up @@ -978,16 +979,10 @@ Pathfinder::isNoRippleOut(STPath const& currentPath)
}

void
addUniquePath(STPathSet& pathSet, STPath const& path)
addUniquePath(STPathSet& pathSet, std::unordered_set<STPath, STPathHash>& index, STPath const& path)
{
// TODO(tom): building an STPathSet this way is quadratic in the size
// of the STPathSet!
for (auto const& p : pathSet)
{
if (p == path)
return;
}
pathSet.pushBack(path);
if (index.insert(path).second)
pathSet.pushBack(path);
}
Comment on lines 981 to 986

void
Expand Down Expand Up @@ -1021,7 +1016,7 @@ Pathfinder::addLink(
{ // non-default path to XRP destination
JLOG(j_.trace()) << "complete path found ax: "
<< currentPath.getJson(JsonOptions::KNone);
addUniquePath(completePaths_, currentPath);
addUniquePath(completePaths_, completePathsIndex_, currentPath);
}
}
else
Expand Down Expand Up @@ -1124,7 +1119,8 @@ Pathfinder::addLink(
{
JLOG(j_.trace()) << "complete path found ae: "
<< currentPath.getJson(JsonOptions::KNone);
addUniquePath(completePaths_, currentPath);
addUniquePath(
completePaths_, completePathsIndex_, currentPath);
}
}
else if (!bDestOnly)
Expand Down Expand Up @@ -1255,7 +1251,7 @@ Pathfinder::addLink(
// complete
JLOG(j_.trace()) << "complete path found bx: "
<< currentPath.getJson(JsonOptions::KNone);
addUniquePath(completePaths_, newPath);
addUniquePath(completePaths_, completePathsIndex_, newPath);
}
else
{
Expand Down Expand Up @@ -1301,7 +1297,7 @@ Pathfinder::addLink(
// complete
JLOG(j_.trace()) << "complete path found ba: "
<< currentPath.getJson(JsonOptions::KNone);
addUniquePath(completePaths_, newPath);
addUniquePath(completePaths_, completePathsIndex_, newPath);
}
else
{
Expand Down
15 changes: 15 additions & 0 deletions src/xrpld/rpc/detail/Pathfinder.h
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Original file line number Diff line number Diff line change
Expand Up @@ -10,8 +10,22 @@
#include <xrpl/protocol/STAmount.h>
#include <xrpl/protocol/STPathSet.h>

#include <unordered_set>

namespace xrpl {

struct STPathHash
{
std::size_t
operator()(STPath const& path) const noexcept
{
std::size_t h = path.size();
for (auto const& elem : path)
h ^= elem.hash() + 0x9e3779b9 + (h << 6) + (h >> 2);
return h;
}
};
Comment on lines +17 to +27

/** Calculates payment paths.

The @ref RippleCalc determines the quality of the found paths.
Expand Down Expand Up @@ -187,6 +201,7 @@ class Pathfinder : public CountedObject<Pathfinder>

STPathElement source_;
STPathSet completePaths_;
std::unordered_set<STPath, STPathHash> completePathsIndex_;
Comment on lines 202 to +204
std::vector<PathRank> pathRanks_;
std::map<PathType, STPathSet> paths_;

Expand Down
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