1 files changed, 105 insertions, 0 deletions
diff --git a/src/rocksdb/util/random_test.cc b/src/rocksdb/util/random_test.cc
new file mode 100644
index 000000000..ad5208193
--- /dev/null
+++ b/src/rocksdb/util/random_test.cc
@@ -0,0 +1,105 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+// Copyright (c) 2012 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+
+#include <cstring>
+#include <vector>
+
+#include "test_util/testharness.h"
+#include "util/random.h"
+
+using ROCKSDB_NAMESPACE::Random;
+
+TEST(RandomTest, Uniform) {
+  const int average = 20;
+  for (uint32_t seed : {0, 1, 2, 37, 4096}) {
+    Random r(seed);
+    for (int range : {1, 2, 8, 12, 100}) {
+      std::vector<int> counts(range, 0);
+
+      for (int i = 0; i < range * average; ++i) {
+        ++counts.at(r.Uniform(range));
+      }
+      int max_variance = static_cast<int>(std::sqrt(range) * 2 + 4);
+      for (int i = 0; i < range; ++i) {
+        EXPECT_GE(counts[i], std::max(1, average - max_variance));
+        EXPECT_LE(counts[i], average + max_variance + 1);
+      }
+    }
+  }
+}
+
+TEST(RandomTest, OneIn) {
+  Random r(42);
+  for (int range : {1, 2, 8, 12, 100, 1234}) {
+    const int average = 100;
+    int count = 0;
+    for (int i = 0; i < average * range; ++i) {
+      if (r.OneIn(range)) {
+        ++count;
+      }
+    }
+    if (range == 1) {
+      EXPECT_EQ(count, average);
+    } else {
+      int max_variance = static_cast<int>(std::sqrt(average) * 1.5);
+      EXPECT_GE(count, average - max_variance);
+      EXPECT_LE(count, average + max_variance);
+    }
+  }
+}
+
+TEST(RandomTest, OneInOpt) {
+  Random r(42);
+  for (int range : {-12, 0, 1, 2, 8, 12, 100, 1234}) {
+    const int average = 100;
+    int count = 0;
+    for (int i = 0; i < average * range; ++i) {
+      if (r.OneInOpt(range)) {
+        ++count;
+      }
+    }
+    if (range < 1) {
+      EXPECT_EQ(count, 0);
+    } else if (range == 1) {
+      EXPECT_EQ(count, average);
+    } else {
+      int max_variance = static_cast<int>(std::sqrt(average) * 1.5);
+      EXPECT_GE(count, average - max_variance);
+      EXPECT_LE(count, average + max_variance);
+    }
+  }
+}
+
+TEST(RandomTest, PercentTrue) {
+  Random r(42);
+  for (int pct : {-12, 0, 1, 2, 10, 50, 90, 98, 99, 100, 1234}) {
+    const int samples = 10000;
+
+    int count = 0;
+    for (int i = 0; i < samples; ++i) {
+      if (r.PercentTrue(pct)) {
+        ++count;
+      }
+    }
+    if (pct <= 0) {
+      EXPECT_EQ(count, 0);
+    } else if (pct >= 100) {
+      EXPECT_EQ(count, samples);
+    } else {
+      int est = (count * 100 + (samples / 2)) / samples;
+      EXPECT_EQ(est, pct);
+    }
+  }
+}
+
+int main(int argc, char** argv) {
+  ::testing::InitGoogleTest(&argc, argv);
+
+  return RUN_ALL_TESTS();
+}