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feat: use Kahn's algorithm for finding toposort #312

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merged 10 commits into from
Jan 3, 2025
Merged

feat: use Kahn's algorithm for finding toposort #312

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4c518e6
feat: use Kahn's algorithm for finding toposort
winprn Jan 2, 2025
2172163
fix: only consider vertices in current subgraph
winprn Jan 2, 2025
9e7190e
fix: update test to reflect latest implementation
winprn Jan 2, 2025
8a04a58
improv: make BFS faster
winprn Jan 2, 2025
f825dff
Revert "fix: update test to reflect latest implementation"
winprn Jan 2, 2025
72fcded
apply suggestion
winprn Jan 2, 2025
3f2f951
fix: revert changes in comment
winprn Jan 2, 2025
2c0f722
improv: speed up vertex checking
winprn Jan 2, 2025
5adaf37
apply suggestions
winprn Jan 2, 2025
d040be7
improv: remove DFS from codebase
winprn Jan 3, 2025
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49 changes: 47 additions & 2 deletions packages/object/src/hashgraph/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -256,14 +256,59 @@ export class HashGraph {
return result;
}

kahnAlgorithm(origin: Hash, subgraph: ObjectSet<Hash>): Hash[] {
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const result: Hash[] = [];
const inDegree = new Map<Hash, number>();
const queue: Hash[] = [];

for (const hash of subgraph.entries()) {
inDegree.set(hash, 0);
}

for (const [_, children] of this.forwardEdges) {
for (const child of children) {
inDegree.set(child, (inDegree.get(child) || 0) + 1);
}
}
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let head = 0;
queue.push(origin);
while (queue.length > 0) {
const current = queue[head];
head++;
if (!current) continue;

result.push(current);

for (const child of this.forwardEdges.get(current) || []) {
if (!subgraph.has(child)) continue;
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const inDegreeValue = inDegree.get(child);
if (inDegreeValue === undefined) {
log.error("::hashgraph::Kahn: Undefined in-degree value");
return [];
}
inDegree.set(child, inDegreeValue - 1);
if (inDegree.get(child) === 0) {
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queue.push(child);
}
}

if (head > queue.length / 2) {
queue.splice(0, head);
head = 0;
}
}

return result;
}

/* Topologically sort the vertices in the whole hashgraph or the past of a given vertex. */
topologicalSort(
updateBitsets = false,
origin: Hash = HashGraph.rootHash,
subgraph: ObjectSet<Hash> = new ObjectSet(this.vertices.keys()),
): Hash[] {
const result = this.depthFirstSearch(origin, subgraph);
result.reverse();
const result = this.kahnAlgorithm(origin, subgraph);
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if (!updateBitsets) return result;
this.reachablePredecessors.clear();
this.topoSortedIndex.clear();
Expand Down
18 changes: 9 additions & 9 deletions packages/object/tests/hashgraph.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -49,8 +49,8 @@ describe("HashGraph construction tests", () => {

const linearOps = obj2.hashGraph.linearizeOperations();
expect(linearOps).toEqual([
{ type: "add", value: 1 },
{ type: "add", value: 2 },
{ type: "add", value: 1 },
]);
});

Expand Down Expand Up @@ -170,8 +170,8 @@ describe("HashGraph for AddWinSet tests", () => {
const linearOps = obj1.hashGraph.linearizeOperations();
expect(linearOps).toEqual([
{ type: "add", value: 1 },
{ type: "add", value: 2 },
{ type: "remove", value: 1 },
{ type: "add", value: 2 },
]);
});

Expand Down Expand Up @@ -204,8 +204,8 @@ describe("HashGraph for AddWinSet tests", () => {
expect(linearOps).toEqual([
{ type: "add", value: 1 },
{ type: "add", value: 1 },
{ type: "remove", value: 5 },
{ type: "add", value: 10 },
{ type: "remove", value: 5 },
]);
});

Expand Down Expand Up @@ -235,9 +235,9 @@ describe("HashGraph for AddWinSet tests", () => {

const linearOps = obj1.hashGraph.linearizeOperations();
expect(linearOps).toEqual([
{ type: "add", value: 1 },
{ type: "add", value: 1 },
{ type: "add", value: 2 },
{ type: "add", value: 1 },
]);
});

Expand Down Expand Up @@ -288,12 +288,12 @@ describe("HashGraph for AddWinSet tests", () => {

const linearOps = obj1.hashGraph.linearizeOperations();
expect(linearOps).toEqual([
{ type: "add", value: 1 },
{ type: "add", value: 1 },
{ type: "remove", value: 2 },
{ type: "add", value: 2 },
{ type: "add", value: 1 },
{ type: "add", value: 3 },
{ type: "remove", value: 1 },
{ type: "add", value: 3 },
]);
});

Expand Down Expand Up @@ -345,11 +345,11 @@ describe("HashGraph for AddWinSet tests", () => {
const linearOps = obj1.hashGraph.linearizeOperations();
expect(linearOps).toEqual([
{ type: "add", value: 1 },
{ type: "remove", value: 2 },
{ type: "add", value: 1 },
{ type: "remove", value: 2 },
{ type: "add", value: 3 },
{ type: "remove", value: 2 },
{ type: "remove", value: 1 },
{ type: "add", value: 3 },
{ type: "add", value: 2 },
{ type: "remove", value: 1 },
]);
Expand Down Expand Up @@ -602,7 +602,7 @@ describe("Vertex timestamp tests", () => {
test("Test: Vertex's timestamp must not be less than any of its dependencies' timestamps", () => {
/*
__ V1:ADD(1) __
/ \
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/ \
ROOT -- V2:ADD(2) ---- V4:ADD(4) (invalid)
\ /
-- V3:ADD(3) --
Expand Down
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