statistical_filter.cc

这是一个著名的应用层组播中间件的源码

//Copyright (c) 2004, Charles Killian, Adolfo Rodriguez, Dejan Kostic, Sooraj Bhat, and Amin Vahdat
//All rights reserved.
//
//Redistribution and use in source and binary forms, with or without
//modification, are permitted provided that the following conditions are met:
//
//   * Redistributions of source code must retain the above copyright
//     notice, this list of conditions and the following disclaimer.
//   * Redistributions in binary form must reproduce the above copyright
//     notice, this list of conditions and the following disclaimer in
//     the documentation and/or other materials provided with the
//     distribution.
//   * Neither the names of Duke University nor The University of
//     California, San Diego, nor the names of its contributors
//     may be used to endorse or promote products derived from
//     this software without specific prior written permission.
//
//THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
//AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
//IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
//DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
//FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
//DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
//SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
//CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
//OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
//USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "statistical_filter.h"
#include "stdio.h"
#include <math.h>

statistical_filter::statistical_filter(int history)
  :measurements( 0), total( 0), total_square( 0),standard_deviation (0),keep_history(history)
{
}
statistical_filter::~statistical_filter()
{
}

// ---------------------------------------------- 
// update
// ---------------------------------------------- 

void  statistical_filter::update (double incoming)
{
  total+= incoming;
  total_square+= incoming*incoming;
  measurements ++;
  standard_deviation =sqrt( 
			   (total_square* measurements-
			    (total*total))/
			   ( measurements*( measurements - 1))
			   );
  value =total/( double)measurements;
//  printf("statistical_value: %lf, incoming  %lf\n", 
//         value, incoming);
  if (keep_history)
    {
      contents.insert( incoming);
    }
}

// ---------------------------------------------- 
// get_deviation
// ---------------------------------------------- 

 double  statistical_filter::get_deviation ()
{
  return standard_deviation;
}

// ---------------------------------------------- 
// get_percentile
// ---------------------------------------------- 

double  statistical_filter::get_percentile (double rank)
{

  if (rank < 0 || rank > 1.0)
    {
      fprintf(stderr, "get_percentile invalid rank: %d\n", rank);
      return -1;
    }
  if (!keep_history)
    {
      fprintf(stderr, "get_percentile not maintaining history: %d\n", keep_history);
      return -1;
    }
  if (contents.size() == 0)
    {
      //      fprintf(stderr, " get_percentilecontents.size(): %d\n", contents.size());
      return -1;
    }

  int which = (int)((double)(contents.size()-1)*rank); //The -1 is because it is 0 indexed 
  //printf("which: %d out of %d %f \n", which, contents.size(), rank);

  set<double, less<double> >::const_iterator element;
  int counter = 0;
  for(element=contents.begin();element!=contents.end();element++)
    {
      //printf("looking at %f (%d) -- ", *element, counter);
      if (counter == which)
	{
	  return *element;
	}
      counter++;
    }
  //somehow we got here, return the largest value
  return *((contents.end())--);
}

// ---------------------------------------------- 
// get_count
// ---------------------------------------------- 

int  statistical_filter::get_count ()
{
  return measurements;
}

// ---------------------------------------------- 
// reset
// ---------------------------------------------- 

int  statistical_filter::reset ()
{
  measurements = 0;
  value = 0;
  total = 0;
  total_square = 0;
  standard_deviation= 0;
  contents.clear();
}