SF: Adding statistical mode
- Adding statistical mode for timestamp intervals.
- Moving math calculations into util class, and adding a unit test.
See go/surface-flinger-scheduler for more info and systrace links.
Test: SF tests pass. Adding new test class.
Bug: 113612090
Change-Id: I3c3a73e3d8719e47326d8a48d27683037b7beb47
diff --git a/services/surfaceflinger/Scheduler/SchedulerUtils.cpp b/services/surfaceflinger/Scheduler/SchedulerUtils.cpp
new file mode 100644
index 0000000..191022d
--- /dev/null
+++ b/services/surfaceflinger/Scheduler/SchedulerUtils.cpp
@@ -0,0 +1,56 @@
+/*
+ * Copyright 2018 The Android Open Source Project
+ *
+ * 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 "SchedulerUtils.h"
+
+#include <cinttypes>
+#include <numeric>
+#include <unordered_map>
+#include <vector>
+
+namespace android {
+namespace scheduler {
+
+int64_t calculate_median(std::vector<int64_t>* v) {
+ if (!v || v->empty()) {
+ return 0;
+ }
+
+ size_t n = v->size() / 2;
+ nth_element(v->begin(), v->begin() + n, v->end());
+ return v->at(n);
+}
+
+int64_t calculate_mode(const std::vector<int64_t>& v) {
+ if (v.empty()) {
+ return 0;
+ }
+
+ // Create a map with all the counts for the indivicual values in the vector.
+ std::unordered_map<int64_t, int64_t> counts;
+ for (int64_t value : v) {
+ counts[value]++;
+ }
+
+ // Sort the map, and return the number with the highest count. If two numbers have
+ // the same count, first one is returned.
+ using ValueType = const decltype(counts)::value_type&;
+ const auto compareCounts = [](ValueType l, ValueType r) { return l.second <= r.second; };
+ return std::max_element(counts.begin(), counts.end(), compareCounts)->first;
+}
+
+} // namespace scheduler
+} // namespace android