1 files changed, 75 insertions, 0 deletions
diff --git a/include/cpustats/CentralTendencyStatistics.h b/include/cpustats/CentralTendencyStatistics.h
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+++ b/include/cpustats/CentralTendencyStatistics.h
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+/*
+ * Copyright (C) 2011 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.
+ */
+
+#ifndef _CENTRAL_TENDENCY_STATISTICS_H
+#define _CENTRAL_TENDENCY_STATISTICS_H
+
+#include <math.h>
+
+// Not multithread safe
+class CentralTendencyStatistics {
+
+public:
+
+    CentralTendencyStatistics() :
+            mMean(NAN), mMedian(NAN), mMinimum(INFINITY), mMaximum(-INFINITY), mN(0), mM2(0),
+            mVariance(NAN), mVarianceKnownForN(0), mStddev(NAN), mStddevKnownForN(0) { }
+
+    ~CentralTendencyStatistics() { }
+
+    // add x to the set of samples
+    void sample(double x);
+
+    // return the arithmetic mean of all samples so far
+    double mean() const { return mMean; }
+
+    // return the minimum of all samples so far
+    double minimum() const { return mMinimum; }
+
+    // return the maximum of all samples so far
+    double maximum() const { return mMaximum; }
+
+    // return the variance of all samples so far
+    double variance() const;
+
+    // return the standard deviation of all samples so far
+    double stddev() const;
+
+    // return the number of samples added so far
+    unsigned n() const { return mN; }
+
+    // reset the set of samples to be empty
+    void reset();
+
+private:
+    double mMean;
+    double mMedian;
+    double mMinimum;
+    double mMaximum;
+    unsigned mN;    // number of samples so far
+    double mM2;
+
+    // cached variance, and n at time of caching
+    mutable double mVariance;
+    mutable unsigned mVarianceKnownForN;
+
+    // cached standard deviation, and n at time of caching
+    mutable double mStddev;
+    mutable unsigned mStddevKnownForN;
+
+};
+
+#endif // _CENTRAL_TENDENCY_STATISTICS_H