| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // 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 |
| // "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: |
| /// 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 |