From 8d707127988c2a96d0e182ba8e1520a2b466fc18 Mon Sep 17 00:00:00 2001
From: Gloria Mundi <gloria@gloria-mundi.eu>
Date: Thu, 13 Feb 2025 21:53:53 +0100
Subject: dinic/capacity scaling: remove dinic.cpp, add comment to
 dinicScaling.cpp

---
 content/graph/dinic.cpp        | 55 -------------------------------------
 content/graph/dinicScaling.cpp |  1 +
 test/graph/dinic.cpp           | 62 ------------------------------------------
 3 files changed, 1 insertion(+), 117 deletions(-)
 delete mode 100644 content/graph/dinic.cpp
 delete mode 100644 test/graph/dinic.cpp

diff --git a/content/graph/dinic.cpp b/content/graph/dinic.cpp
deleted file mode 100644
index c8c34a8..0000000
--- a/content/graph/dinic.cpp
+++ /dev/null
@@ -1,55 +0,0 @@
-struct Edge {
-	int to, rev;
-	ll f, c;
-};
-
-vector<vector<Edge>> adj;
-int s, t;
-vector<int> pt, dist;
-
-void addEdge(int u, int v, ll c) {
-	adj[u].push_back({v, (int)ssize(adj[v]), 0, c});
-	adj[v].push_back({u, (int)ssize(adj[u]) - 1, 0, 0});
-}
-
-bool bfs() {
-	dist.assign(ssize(adj), -1);
-	dist[s] = 0;
-	queue<int> q({s});
-	while (!q.empty() && dist[t] < 0) {
-		int v = q.front(); q.pop();
-		for (Edge& e : adj[v]) {
-			if (dist[e.to] < 0 && e.c - e.f > 0) {
-				dist[e.to] = dist[v] + 1;
-				q.push(e.to);
-	}}}
-	return dist[t] >= 0;
-}
-
-ll dfs(int v, ll flow = INF) {
-	if (v == t || flow == 0) return flow;
-	for (; pt[v] < ssize(adj[v]); pt[v]++) {
-		Edge& e = adj[v][pt[v]];
-		if (dist[e.to] != dist[v] + 1) continue;
-		ll cur = dfs(e.to, min(e.c - e.f, flow));
-		if (cur > 0) {
-			e.f += cur;
-			adj[e.to][e.rev].f -= cur;
-			return cur;
-	}}
-	return 0;
-}
-
-ll maxFlow(int source, int target) {
-	s = source, t = target;
-	ll flow = 0;
-	while (bfs()) {
-		pt.assign(ssize(adj), 0);
-		ll cur;
-		do {
-			cur = dfs(s);
-			flow += cur;
-		} while (cur > 0);
-	}
-	return flow;
-}
diff --git a/content/graph/dinicScaling.cpp b/content/graph/dinicScaling.cpp
index 0082c05..fd82296 100644
--- a/content/graph/dinicScaling.cpp
+++ b/content/graph/dinicScaling.cpp
@@ -43,6 +43,7 @@ ll dfs(int v, ll flow) {
 ll maxFlow(int source, int target) {
 	s = source, t = target;
 	ll flow = 0;
+	// lim = 1 may be faster if capacities are small
 	for (ll lim = (1LL << 62); lim >= 1; lim /= 2) {
 		while (bfs(lim)) {
 			pt.assign(ssize(adj), 0);
diff --git a/test/graph/dinic.cpp b/test/graph/dinic.cpp
deleted file mode 100644
index 5af7c6f..0000000
--- a/test/graph/dinic.cpp
+++ /dev/null
@@ -1,62 +0,0 @@
-#include "../util.h"
-constexpr ll INF = LL::INF;
-namespace dinic {
-#include <graph/dinic.cpp>
-}
-
-namespace pushRelabel {
-#include <graph/pushRelabel.cpp>
-}
-
-void stress_test() {
-	ll queries = 0;
-	for (int tries = 0; tries < 20'000; tries++) {
-		int n = Random::integer<int>(2, 30);
-		int m = Random::integer<int>(n-1, max<int>(n, min<int>(500, n*(n-1) / 2 + 1)));
-
-		dinic::adj.assign(n, {});
-		pushRelabel::adj.assign(n, {});
-
-		Graph<NoData, true> g(n);
-		g.erdosRenyi(m);
-		g.forEdges([](int a, int b){
-			ll w = Random::integer<ll>(1, 1'000'000'000'000ll);
-			dinic::addEdge(a, b, w);
-			pushRelabel::addEdge(a, b, w);
-		});
-
-		ll got = dinic::maxFlow(0, n - 1);
-		ll expected = pushRelabel::maxFlow(0, n - 1);
-		
-		if (got != expected) cerr << "got: " << got << ", expected: " << expected << FAIL;
-		queries += n;
-	}
-	cerr << "tested random queries: " << queries << endl;
-}
-
-constexpr int N = 50000;
-constexpr int M = 200000;
-void performance_test() {
-	using namespace dinic;
-	timer t;
-	Graph<NoData> g(N);
-	g.erdosRenyi(M);
-	adj.assign(N, {});
-	g.forEdges([](int a, int b){
-		ll w1 = Random::integer<ll>(1, 1'000'000'000'000ll);
-		ll w2 = Random::integer<ll>(1, 1'000'000'000'000ll);
-		addEdge(a, b, w1);
-		addEdge(b, a, w2);
-	});
-
-	t.start();
-	hash_t hash = maxFlow(0, N - 1);
-	t.stop();
-	if (t.time > 2000) cerr << "too slow: " << t.time << FAIL;
-	cerr << "tested performance: " << t.time << "ms (hash: " << hash << ")" << endl;
-}
-
-int main() {
-	stress_test();
-	performance_test();
-}
-- 
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