be/src/util/stat-util.h

// Licensed to the Apache Software Foundation (ASF) under one
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// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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
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// under the License.


#ifndef IMPALA_UTIL_STAT_UTIL_H
#define IMPALA_UTIL_STAT_UTIL_H

#include <math.h>

namespace impala {

class StatUtil {
 public:
  /// Computes mean and standard deviation
  template <typename T>
  static void ComputeMeanStddev(const T* values, int N, double* mean, double* stddev) {
    *mean = 0;
    *stddev = 0;

    for (int i = 0; i < N; ++i) {
      *mean += values[i];
    }
    *mean /= N;

    for (int i = 0; i < N; ++i) {
      double d = values[i] - *mean;
      *stddev += d*d;
    }

    *stddev /= N;
    *stddev = sqrt(*stddev);
  }
};

}

#endif