add llvm::SmallVector to paddle (#34832)

* add llvm::SmallVector to paddle

* rename small vector file

* merge paddle small vector to one file

* add small_vector_test

* modify smallvector test argument type

* add string header

paddle/testing/CMakeLists.txt

@@ -3,3 +3,4 @@
 if(WITH_TESTING)
   cc_library(paddle_gtest_main SRCS paddle_gtest_main.cc DEPS device_context memory gtest gflags)
 endif()
+cc_test(small_vector_test SRCS small_vector_test.cc DEPS gtest gflags)

paddle/testing/small_vector_test.cc

+// Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+//
+// 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 "paddle/utils/small_vector.h"
+
+#include <cstdlib>
+#include <ctime>
+
+#include "glog/logging.h"
+#include "gtest/gtest.h"
+
+template <typename T, unsigned N>
+static std::vector<T> ToStdVector(const paddle::SmallVector<T, N> &vec) {
+  std::vector<T> std_vec;
+  std_vec.reserve(vec.size());
+  for (size_t i = 0; i < vec.size(); ++i) {
+    std_vec.emplace_back(vec[i]);
+  }
+  return std_vec;
+}
+
+template <size_t N>
+void SmallVectorCheck(size_t n) {
+  std::srand(std::time(nullptr));
+
+  std::vector<int> std_vec;
+  paddle::SmallVector<int, N> vec;
+
+  for (size_t i = 0; i < n; ++i) {
+    int value = rand();  // NOLINT
+
+    std_vec.emplace_back(value);
+    vec.emplace_back(value);
+
+    CHECK_EQ(std_vec.size(), vec.size());
+    CHECK_EQ(std_vec.back(), vec.back());
+
+    CHECK_EQ(vec.back(), value);
+  }
+
+  bool is_equal = (std_vec == ToStdVector(vec));
+
+  CHECK_EQ(is_equal, true);
+
+  for (size_t i = 0; i < n; ++i) {
+    CHECK_EQ(std_vec.size(), vec.size());
+    CHECK_EQ(std_vec.back(), vec.back());
+    std_vec.pop_back();
+    vec.pop_back();
+    CHECK_EQ(std_vec.size(), vec.size());
+  }
+
+  CHECK_EQ(std_vec.size(), static_cast<size_t>(0));
+  CHECK_EQ(vec.size(), static_cast<size_t>(0));
+}
+
+TEST(samll_vector, small_vector) {
+  for (size_t i = 0; i < 20; ++i) {
+    SmallVectorCheck<1>(i);
+    SmallVectorCheck<10>(i);
+    SmallVectorCheck<15>(i);
+    SmallVectorCheck<20>(i);
+    SmallVectorCheck<21>(i);
+    SmallVectorCheck<25>(i);
+  }
+}