1 /*
2 * Copyright 2018 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #pragma once
18
19 #include <chrono>
20 #include <cinttypes>
21 #include <numeric>
22 #include <unordered_map>
23 #include <vector>
24
25 namespace android {
26 namespace scheduler {
27 using namespace std::chrono_literals;
28
29 // This number is used to set the size of the arrays in scheduler that hold information
30 // about layers.
31 static constexpr size_t ARRAY_SIZE = 30;
32
33 // This number is used to have a place holder for when the screen is not NORMAL/ON. Currently
34 // the config is not visible to SF, and is completely maintained by HWC. However, we would
35 // still like to keep track of time when the device is in this config.
36 static constexpr int SCREEN_OFF_CONFIG_ID = -1;
37 static constexpr uint32_t HWC2_SCREEN_OFF_CONFIG_ID = 0xffffffff;
38
39 // This number is used when we try to determine how long does a given layer stay relevant.
40 // Currently it is set to 100ms, because that would indicate 10Hz rendering.
41 static constexpr std::chrono::nanoseconds TIME_EPSILON_NS = 100ms;
42
43 // This number is used when we try to determine how long do we keep layer information around
44 // before we remove it. Currently it is set to 100ms.
45 static constexpr std::chrono::nanoseconds OBSOLETE_TIME_EPSILON_NS = 100ms;
46
47 // Calculates the statistical mean (average) in the data structure (array, vector). The
48 // function does not modify the contents of the array.
49 template <typename T>
calculate_mean(const T & v)50 auto calculate_mean(const T& v) {
51 using V = typename T::value_type;
52 V sum = std::accumulate(v.begin(), v.end(), static_cast<V>(0));
53 return sum / static_cast<V>(v.size());
54 }
55
56 // Calculates the statistical median in the vector. Return 0 if the vector is empty. The
57 // function modifies the vector contents.
58 int64_t calculate_median(std::vector<int64_t>* v);
59
60 // Calculates the statistical mode in the vector. Return 0 if the vector is empty.
61 template <typename T>
calculate_mode(const T & v)62 auto calculate_mode(const T& v) {
63 if (v.empty()) {
64 return 0;
65 }
66
67 // Create a map with all the counts for the indivicual values in the vector.
68 std::unordered_map<int64_t, int> counts;
69 for (int64_t value : v) {
70 counts[value]++;
71 }
72
73 // Sort the map, and return the number with the highest count. If two numbers have
74 // the same count, first one is returned.
75 using ValueType = const decltype(counts)::value_type&;
76 const auto compareCounts = [](ValueType l, ValueType r) { return l.second <= r.second; };
77 return static_cast<int>(std::max_element(counts.begin(), counts.end(), compareCounts)->first);
78 }
79
80 } // namespace scheduler
81 } // namespace android