1 files changed, 39 insertions, 0 deletions
diff --git a/test/math/shortModInv.cpp b/test/math/shortModInv.cpp
new file mode 100644
index 0000000..26960bf
--- /dev/null
+++ b/test/math/shortModInv.cpp
@@ -0,0 +1,39 @@
+#include "../util.h"
+#include <math/shortModInv.cpp>
+
+void stress_test() {
+	ll queries = 0;
+	for (int i = 0; i < 10'000'000; i++) {
+		ll n = Random::integer<ll>(2, 1'000'000'000);
+		ll x = 0;
+		do {
+			x = Random::integer<ll>(0, n);
+		} while (gcd(x, n) != 1);
+		ll y = multInv(x, n);
+		ll got = (x*y) % n;
+		if (got != 1) cerr << "got: " << got << ", expected: 1" << FAIL;
+		queries++;
+	}
+	cerr << "tested queries: " << queries << endl;
+}
+
+constexpr int N = 1'000'000;
+void performance_test() {
+	timer t;
+	hash_t hash = 0;
+	for (int operations = 0; operations < N; operations++) {
+		ll a = Random::integer<ll>(0, 1'000'000'000);
+		ll b = Random::integer<ll>(2, 1'000'000'000);
+		t.start();
+		hash += multInv(a, b);
+		t.stop();
+	}
+	if (t.time > 750) cerr << "too slow: " << t.time << FAIL;
+	cerr << "tested performance: " << t.time << "ms (hash: " << hash << ")" << endl;
+}
+
+int main() {
+	stress_test();
+	performance_test();
+}
+