1 files changed, 53 insertions, 0 deletions
diff --git a/test/math/linearCongruence.cpp b/test/math/linearCongruence.cpp
new file mode 100644
index 0000000..ba8eeac
--- /dev/null
+++ b/test/math/linearCongruence.cpp
@@ -0,0 +1,53 @@
+#include "../util.h"
+#include <math/extendedEuclid.cpp>
+#include <math/multInv.cpp>
+#include <math/linearCongruence.cpp>
+
+ll naive(ll a, ll b, ll m) {
+	for (ll x = 0; x < m; x++) {
+		if ((a * x) % m == b) return x;
+	}
+	return -1;
+}
+
+void stress_test() {
+	ll work = 0;
+	ll positive = 0;
+	for (ll tries = 0; tries < 500'000; tries++) {
+		ll m = Random::integer<ll>(0, 1'000);
+		ll a = Random::integer<ll>(0, m);
+		ll b = Random::integer<ll>(0, m);
+
+		ll got = solveLinearCongruence(a, b, m);
+		ll expected = naive(a, b, m);
+
+		if (got != expected) cerr << "got: " << got << ", expected: " << expected << endl;
+		work++;
+		if (got >= 0) positive++;
+	}
+	cerr << "stress tested: " << work << " (" << positive << ")" << endl;
+}
+
+constexpr int N = 500'000;
+void performance_test() {
+	timer t;
+	hash_t hash = 0;
+	for (int operations = 0; operations < N; operations++) {
+		ll m = Random::integer<ll>(0, 1'0000'000'000);
+		ll a = Random::integer<ll>(0, m);
+		ll b = Random::integer<ll>(0, m);
+
+		t.start();
+		hash += solveLinearCongruence(a, b, m);
+		t.stop();
+	}
+	if (t.time > 500) cerr << "too slow: " << t.time << FAIL;
+	cerr << "tested performance: " << t.time << "ms (hash: " << hash << ")" << endl;
+}
+
+
+int main() {
+	stress_test();
+	performance_test();
+}
+