chore: import upstream snapshot with attribution

paddle/phi/kernels/funcs/algorithm.h

@@ -0,0 +1,88 @@
+// 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.
+
+#pragma once
+
+#include <algorithm>
+#include <cstdint>  // for int64_t
+#include <numeric>
+
+#include "paddle/common/hostdevice.h"
+
+namespace phi {
+namespace funcs {
+
+template <typename T>
+HOSTDEVICE inline int64_t BinarySearch(const T *x, int64_t num, const T &val) {
+  int64_t beg = 0, end = num - 1;
+  while (beg <= end) {
+    auto mid = ((beg + end) >> 1);
+    if (x[mid] == val)
+      return mid;
+    else if (x[mid] < val)
+      beg = mid + 1;
+    else
+      end = mid - 1;
+  }
+  return -1;
+}
+
+template <typename T1, typename T2>
+HOSTDEVICE inline size_t LowerBound(const T1 *x, size_t num, const T2 &val) {
+#if defined(__CUDA_ARCH__) || defined(__HIPCC__)  // @{ Group LowerBound
+  // The following code is from
+  // https://en.cppreference.com/w/cpp/algorithm/lower_bound
+  auto *first = x;
+  int64_t count = static_cast<int64_t>(num);
+  while (count > 0) {
+    int64_t step = (count >> 1);
+    auto *it = first + step;
+    if (*it < val) {
+      first = ++it;
+      count -= (step + 1);
+    } else {
+      count = step;
+    }
+  }
+  return static_cast<size_t>(first - x);
+#else
+  return static_cast<size_t>(std::lower_bound(x, x + num, val) - x);
+#endif  // @} End Group LowerBound
+}
+
+template <typename T1, typename T2>
+HOSTDEVICE inline size_t UpperBound(const T1 *x, size_t num, const T2 &val) {
+#if defined(__CUDA_ARCH__) || defined(__HIPCC__)  // @{ Group UpperBound
+  // The following code is from
+  // https://en.cppreference.com/w/cpp/algorithm/upper_bound
+  auto *first = x;
+  int64_t count = static_cast<int64_t>(num);
+  while (count > 0) {
+    auto step = (count >> 1);
+    auto *it = first + step;
+    if (val < *it) {
+      count = step;
+    } else {
+      first = ++it;
+      count -= (step + 1);
+    }
+  }
+  return static_cast<size_t>(first - x);
+#else
+  return static_cast<size_t>(std::upper_bound(x, x + num, val) - x);
+#endif  // @} End Group UpperBound
+}
+
+}  // namespace funcs
+}  // namespace phi