add test for modint / convolution

Author: yosupo06

test/unittest/convolution_test.cpp

@@ -385,3 +385,34 @@ TEST(ConvolutionTest, Conv18433) {
 
     ASSERT_EQ(conv_naive<MOD>(a, b), convolution<MOD>(a, b));
 }
+
+TEST(ConvolutionTest, Conv2) {
+    std::vector<ll> empty = {};
+    ASSERT_EQ(empty, convolution<2>(empty, empty));
+}
+
+TEST(ConvolutionTest, Conv2147483647) {
+    const int MOD = 2147483647;
+    using mint = static_modint<MOD>;
+    std::vector<mint> a(1), b(2);
+    for (int i = 0; i < 1; i++) {
+        a[i] = randint(0, MOD - 1);
+    }
+    for (int i = 0; i < 2; i++) {
+        b[i] = randint(0, MOD - 1);
+    }
+    ASSERT_EQ(conv_naive(a, b), convolution(a, b));
+}
+
+TEST(ConvolutionTest, Conv2130706433) {
+    const int MOD = 2130706433;
+    using mint = static_modint<MOD>;
+    std::vector<mint> a(1024), b(1024);
+    for (int i = 0; i < 1024; i++) {
+        a[i] = randint(0, MOD - 1);
+    }
+    for (int i = 0; i < 1024; i++) {
+        b[i] = randint(0, MOD - 1);
+    }
+    ASSERT_EQ(conv_naive(a, b), convolution(a, b));
+}

test/unittest/modint_test.cpp

@@ -100,6 +100,29 @@ TEST(ModintTest, Mod1) {
     ASSERT_EQ(0, mint(true).val());
 }
 
+TEST(ModintTest, ModIntMax) {
+    modint::set_mod(INT32_MAX);
+    for (int i = 0; i < 100; i++) {
+        for (int j = 0; j < 100; j++) {
+            ASSERT_EQ((modint(i) * modint(j)).val(), i * j);
+        }
+    }
+    ASSERT_EQ((modint(1234) + modint(5678)).val(), 1234 + 5678);
+    ASSERT_EQ((modint(1234) - modint(5678)).val(), INT32_MAX - 5678 + 1234);
+    ASSERT_EQ((modint(1234) * modint(5678)).val(), 1234 * 5678);
+
+    using mint = static_modint<INT32_MAX>;
+    for (int i = 0; i < 100; i++) {
+        for (int j = 0; j < 100; j++) {
+            ASSERT_EQ((mint(i) * mint(j)).val(), i * j);
+        }
+    }
+    ASSERT_EQ((mint(1234) + mint(5678)).val(), 1234 + 5678);
+    ASSERT_EQ((mint(1234) - mint(5678)).val(), INT32_MAX - 5678 + 1234);
+    ASSERT_EQ((mint(1234) * mint(5678)).val(), 1234 * 5678);
+    ASSERT_EQ((mint(INT32_MAX) + mint(INT32_MAX)).val(), 0);
+}
+
 #ifndef _MSC_VER
 
 TEST(ModintTest, Int128) {
@@ -158,6 +181,13 @@ TEST(ModintTest, Inv) {
         int x = modint(i).inv().val();
         ASSERT_EQ(1, (ll(x) * i) % 1'000'000'008);
     }
+
+    modint::set_mod(INT32_MAX);
+    for (int i = 1; i < 100000; i++) {
+        if (gcd(i, INT32_MAX) != 1) continue;
+        int x = modint(i).inv().val();
+        ASSERT_EQ(1, (ll(x) * i) % INT32_MAX);
+    }
 }
 
 TEST(ModintTest, ConstUsage) {