feat: Add T-Digest data structure (#11665)

Summary:
Pull Request resolved: #11665

Add the T-Digest data structure implementation to be used in T-Digest
related functions.  Also extract the `getRandomSeed` test utility that is used
in multiple unit tests.

Reviewed By: kagamiori

Differential Revision: D66435741

fbshipit-source-id: 67b1775ad510920cb53b71950a26407fa2c64121

velox/common/testutil/CMakeLists.txt

@@ -12,8 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-velox_add_library(velox_test_util ScopedTestTime.cpp TestValue.cpp)
-velox_link_libraries(velox_test_util PUBLIC velox_exception)
+velox_add_library(velox_test_util ScopedTestTime.cpp TestValue.cpp
+                  RandomSeed.cpp)
+
+velox_link_libraries(
+  velox_test_util
+  PUBLIC velox_exception
+  PRIVATE glog::glog Folly::folly)
 
 if(${VELOX_BUILD_TESTING})
   velox_add_library(velox_test_output_matcher OutputMatcher.cpp)

velox/common/testutil/RandomSeed.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "velox/common/testutil/RandomSeed.h"
+
+#include <folly/Conv.h>
+#include <folly/Random.h>
+#include <glog/logging.h>
+
+#include <cstdlib>
+
+namespace facebook::velox::common::testutil {
+
+bool useRandomSeed() {
+  const char* env = getenv("VELOX_TEST_USE_RANDOM_SEED");
+  return env && folly::to<bool>(env);
+}
+
+unsigned getRandomSeed(unsigned fixedValue) {
+  if (!useRandomSeed()) {
+    return fixedValue;
+  }
+  auto seed = folly::Random::secureRand32();
+  LOG(INFO) << "Random seed: " << seed;
+  return seed;
+}
+
+} // namespace facebook::velox::common::testutil

velox/common/testutil/RandomSeed.h

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+namespace facebook::velox::common::testutil {
+
+/// Get a truely random seed and log it for future reproducing if
+/// VELOX_TEST_USE_RANDOM_SEED is set.  Otherwise return a fixed value so test
+/// runs are deterministic.  We use environment variable because `buck test`
+/// does not allow pass in command line arguments.
+unsigned getRandomSeed(unsigned fixedValue);
+
+bool useRandomSeed();
+
+} // namespace facebook::velox::common::testutil

velox/dwio/common/tests/utils/E2EFilterTestBase.h

@@ -16,6 +16,7 @@
 
 #pragma once
 
+#include "velox/common/testutil/RandomSeed.h"
 #include "velox/common/time/Timer.h"
 #include "velox/dwio/common/BufferedInput.h"
 #include "velox/dwio/common/FileSink.h"
@@ -102,20 +103,10 @@ class E2EFilterTestBase : public testing::Test {
     memory::MemoryManager::testingSetInstance({});
   }
 
-  static bool useRandomSeed() {
-    // Check environment variable because `buck test` does not allow pass in
-    // command line arguments.
-    const char* env = getenv("VELOX_TEST_USE_RANDOM_SEED");
-    return !env ? false : folly::to<bool>(env);
-  }
-
   void SetUp() override {
     rootPool_ = memory::memoryManager()->addRootPool("E2EFilterTestBase");
     leafPool_ = rootPool_->addLeafChild("E2EFilterTestBase");
-    if (useRandomSeed()) {
-      seed_ = folly::Random::secureRand32();
-      LOG(INFO) << "Random seed: " << seed_;
-    }
+    seed_ = common::testutil::getRandomSeed(seed_);
   }
 
   static bool typeKindSupportsValueHook(TypeKind kind) {