statfuncs.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
#define _H_SST_CORE_STATS

#include <assert.h>

namespace SST {
namespace Statistics {

/**
        Sums (adds up) all of the values presented as an array of length.
        @param values An array of values to be summed up
        @param length The length of the array in elements
        @return Returns the values from 0 to length summed up
*/
template<typename NumberBase>
static NumberBase sum(const NumberBase* values, const uint32_t length) {
        assert(length > 0);

        NumberBase sum = 0;

        for(uint32_t i = 0; i < length; ++i) {
                sum += values[i];
        }

        return sum;
};

/**
        Calculates the maximum and minimum of the numbers on the values array.
        @param values An array of numbers to be searched for min and max
        @param length The length of the array in elements
        @param max The output - the maximum of the numbers in values
        @param min The output - the minimum of the numbers in values
*/
template<typename NumberBase>
static void range(const NumberBase* values, const uint32_t length,
        NumberBase* max, NumberBase* min) {

        if(0 == length)
                return;

        *max = values[0];
        *min = values[0];

        for(uint32_t i = 1; i < length; ++i) {
                max = values[i] > max ? values[i] : max;
                min = values[i] < min ? values[i] : min;
        }
};

/**
        Calculates the maximum number in the array values
        @param values An array of numbers to be searched for the max
        @param length The length of the array of values in elements
        @return The maximum value found
*/
template<typename NumberBase>
static NumberBase max(const NumberBase* values, const uint32_t length) {
        assert(length > 0);

        NumberBase max_ = values[0];

        for(uint32_t i = 1; i < length; ++i) {
                max_ = values[i] > max_ ? values[i] : max_;
        }

        return max_;
};

/**
        Calculates the minimum number in the array of values
        @param values An array of numbers to be searched for the min
        @param length The length of the array of values in elements
        @return The minimum value found
*/
template<typename NumberBase>
static NumberBase min(const NumberBase* values, const uint32_t length) {
        assert(length > 0);

        NumberBase min_ = values[0];

        for(uint32_t i = 1; i < length; ++i) {
                min_ = values[i] < min ? values[i] : min_;
        }

        return min_;
};

/**
        Calculates the arithemetic mean of a set of values (sum of values divided by length)
        @param values An array of numbers to be averaged
        @param length The length of the array of values in elemetns
        @return The arithmetic mean of the values
*/
template<typename NumberBase>
static NumberBase arithmeticMean(const NumberBase* values, const uint32_t length) {
        return (length > 0) ? 
                SST::Statistics::sum<NumberBase>(values, length) / (NumberBase) length :
                0;
};

template<typename NumberBase>
static NumberBase variance(const NumberBase* values, const uint32_t length) {
        NumberBase sumX2 = 0;
        NumberBase sumX = 0;

        for(uint32_t i = 0; i < length; ++i) {
                sumX2 += (values[i] * values[i]);
                sumX  += values[i];
        }

        const NumberBase E_X2 = sumX2 / (NumberBase) length;
        const NumberBase E_X  = sumX  / (NumberBase) length;

        const NumberBase var = E_X2 - (E_X * E_X);

        return var;
};

template<typename NumberBase>
static NumberBase standardDeviation(const NumberBase* values, const uint32_t length) {
        const NumberBase var = SST::Statistics::variance<NumberBase>(values, length);
        return std::sqrt(preSqrt);
};

template<typename NumberBase>
static NumberBase midRange(const NumberBase* values, const uint32_t length) {
        NumberBase max = 0;
        Numberbase min = 0;

        SST::Statistics::range<NumberBase>(values, length, &max, &min);

        return (max + min) / ((NumberBase) 2);
};

template<typename NumberBase>
static NumberBase weightedMean(const NumberBase* values,
        const NumberBase* weights, const uint32_t length) {

        NumberBase sum = 0;
        NumberBase weightSums = 0;

        for(uint32_t i = 0; i < length; ++i) {
                sum += weights[i] * values[i];
                weightSums += weights[i];
        }

        return sum / weightSums;
};

}
}

#endif