Merge pull request #32 from atcoder/patch/stress

add simple stress test for twosat,maxflow

Author: yosupo06

test/unittest/maxflow_test.cpp

@@ -4,6 +4,7 @@
 #include <numeric>
 #include <tuple>
 #include <vector>
+#include "../utils/random.hpp"
 
 using namespace atcoder;
 using ll = long long;
@@ -184,4 +185,38 @@ TEST(MaxflowTest, Invalid) {
     // https://github.com/atcoder/ac-library/issues/5
     EXPECT_DEATH(g.flow(0, 0), ".*");
     EXPECT_DEATH(g.flow(0, 0, 0), ".*");
-}
+}
+
+TEST(MaxflowTest, Stress) {
+    for (int phase = 0; phase < 10000; phase++) {
+        int n = randint(2, 20);
+        int m = randint(1, 100);
+        int s, t;
+        std::tie(s, t) = randpair(0, n - 1);
+        if (randbool()) std::swap(s, t);
+
+        mf_graph<int> g(n);
+        for (int i = 0; i < m; i++) {
+            int u = randint(0, n - 1);
+            int v = randint(0, n - 1);
+            int c = randint(0, 10000);
+            g.add_edge(u, v, c);
+        }
+        int flow = g.flow(s, t);
+        int dual = 0;
+        auto cut = g.min_cut(s);
+        std::vector<int> v_flow(n);
+        for (auto e: g.edges()) {
+            v_flow[e.from] -= e.flow;
+            v_flow[e.to] += e.flow;
+            if (cut[e.from] && !cut[e.to]) dual += e.cap;
+        }
+        ASSERT_EQ(flow, dual);
+        ASSERT_EQ(-flow, v_flow[s]);
+        ASSERT_EQ(flow, v_flow[t]);
+        for (int i = 0; i < n; i++) {
+            if (i == s || i == t) continue;
+            ASSERT_EQ(0, v_flow[i]);
+        }
+    }
+}

test/unittest/twosat_test.cpp

@@ -3,6 +3,8 @@
 #include <atcoder/twosat>
 #include <numeric>
 
+#include "../utils/random.hpp"
+
 using namespace atcoder;
 using ll = long long;
 using ull = unsigned long long;
@@ -41,3 +43,43 @@ TEST(TwosatTest, Assign) {
     two_sat ts;
     ts = two_sat(10);
 }
+
+TEST(TwosatTest, StressOK) {
+    for (int phase = 0; phase < 10000; phase++) {
+        int n = randint(1, 20);
+        int m = randint(1, 100);
+        std::vector<bool> expect(n);
+        for (int i = 0; i < n; i++) {
+            expect[i] = randbool();
+        }
+        two_sat ts(n);
+        std::vector<int> xs(m), ys(m), types(m);
+        for (int i = 0; i < m; i++) {
+            int x = randint(0, n - 1);
+            int y = randint(0, n - 1);
+            int type = randint(0, 2);
+            xs[i] = x;
+            ys[i] = y;
+            types[i] = type;
+            if (type == 0) {
+                ts.add_clause(x, expect[x], y, expect[y]);
+            } else if (type == 1) {
+                ts.add_clause(x, !expect[x], y, expect[y]);
+            } else {
+                ts.add_clause(x, expect[x], y, !expect[y]);
+            }
+        }
+        ASSERT_TRUE(ts.satisfiable());
+        auto actual = ts.answer();
+        for (int i = 0; i < m; i++) {
+            int x = xs[i], y = ys[i], type = types[i];
+            if (type == 0) {
+                ASSERT_TRUE(actual[x] == expect[x] || actual[y] == expect[y]);
+            } else if (type == 1) {
+                ASSERT_TRUE(actual[x] != expect[x] || actual[y] == expect[y]);
+            } else {
+                ASSERT_TRUE(actual[x] == expect[x] || actual[y] != expect[y]);
+            }
+        }
+    }
+}

test/utils/random.hpp

@@ -9,6 +9,10 @@ T randint(T a, T b) {
     return std::uniform_int_distribution<T>(a, b)(global_mt19937);
 }
 
+bool randbool() {
+    return randint(0, 1) == 0;
+}
+
 // random choice 2 disjoint elements from [lower, upper]
 template <class T> std::pair<T, T> randpair(T lower, T upper) {
     assert(upper - lower >= 1);