accumulator.h

// Copyright 2009-2016 Sandia Corporation. Under the terms
// of Contract DE-AC04-94AL85000 with Sandia Corporation, the U.S.
// Government retains certain rights in this software.
//
// Copyright (c) 2009-2016, Sandia Corporation
// All rights reserved.
//
// This file is part of the SST software package. For license
// information, see the LICENSE file in the top level directory of the
// distribution.


#ifndef _H_SST_CORE_STATS_ACCUMULATOR
#define _H_SST_CORE_STATS_ACCUMULATOR

#include <sst/core/stats/basestats.h>

namespace SST {
namespace Statistics {

/**
        \class Accumulator

        Allows the online gathering of statistical information about a single quantity. The basic 
        statistics are captured online removing the need to keep a copy of the values of interest.

        @tparam NumberBase A template for the basic numerical type of values
*/
<template typename NumberBase>
class Accumulator : public SST::Statistics::BaseStatistic {

        public:
                /**
                        Create a new Accumulator class with initial values set to a zero count,
                        zero sum statistic of interest.
                */
                Accumulator(char* name) :
                        BaseStatistic(name) {

                        count = 0;
                        sum = 0;
                        sum_sq = 0;
                }

                /**
                        Provides the sum of the values presented so far.
                        @return The sum of values presented to the class so far.
                */
                NumberBase getSum() {
                        return sum;
                }

                /**
                        Provides the sum of each value squared presented to the class so far.
                        @return The sum of squared values presented to the class so far.
                */
                NumberBase getSumSquared() {
                        return sum_sq;
                }

                /**
                        Present a new value to the class to be included in the statistics.
                        @param value New value to be presented
                */
                void add(NumberBase value) {
                        if(enabled) {
                                sum += value;
                                sum_sq += (value * value);
                                count++;
                        }
                }

                /**
                        Present an array of values to the class to be included in the statistics.
                        @param values The array of values to be added to the statistics collection
                        @param length The length of the array being presented
                */
                void add(NumberBase* values, uint32_t length) {
                        if(enabled) {
                                for(uint32_t i = 0; i < length; ++i) {
                                        sum += values[i];
                                        sum_sq += (values[i] * values[i]);
                                }

                                count += (uint64_t) length;
                        }
                }

                /**
                        Get the arithmetic mean of the values presented so far
                        @return The arithmetic mean of the values presented so far.
                */
                NumberBase getArithmeticMean() {
                        return (count > 0) ? (sum / (NumberBase) count) : 0;
                }

                /**
                        Get the variance of the values presented so far
                        @return The variance of the values presented so far
                */
                NumberBase getVariance() {
                        return (count > 0) ?
                                ((sum_sq * count) - (sum * sum)) :
                                0;
                }

                /**
                        Get the standard deviation of the values presented so far
                        @return The standard deviation of the values presented so far
                */
                NumberBase getStandardDeviation() {
                        return (NumberBase) std::sqrt( (double) getVariance() );
                }

                /**
                        Get a count of the number of elements presented to the statistics collection so far.
                        @return Count the number of values presented to the class.
                */
                uint64_t getCount() {
                        return count;
                }

        private:
                NumberBase sum;
                NumberBase sum_sq;
                uint64_t count;

};

}
}

#endif