stat-util.h

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// Copyright 2012 Cloudera Inc.
//
// 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 IMPALA_UTIL_STAT_UTIL_H
#define IMPALA_UTIL_STAT_UTIL_H

#include <math.h>

namespace impala {

class StatUtil {
 public:
  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