processor.cpp

#include "processor.h"
#include "linux_parser.h"

// Return the aggregate CPU utilization
float Processor::Utilization() 
{
  // I have used the algorihm proposed at https://stackoverflow.com/questions/23367857/accurate-calculation-of-cpu-usage-given-in-percentage-in-linux
  
  // Reading to get CPU data
  Processor::cpu_data.push_back(LinuxParser::CpuUtilization());
    
  float first_idle{ 0.0 };
  float first_non_idle{ 0.0 };
  float first_total{ 0.0 };

  float second_idle{ 0.0 };
  float second_non_idle{ 0.0 };
  float second_total{ 0.0 };  
  // These are the indexes for idel and wait quantities
  unsigned const int index_idle{3};
  unsigned const int index_wait{4};

  float consumption {0.0};

  if(cpu_data.size() == 1)
  {
    for(long unsigned int i=0; i<cpu_data[0].size(); ++i)
    {
        if(i==index_idle || i==index_wait)
            first_idle += std::stof(cpu_data[0][i]);
        else
            first_non_idle += std::stof(cpu_data[0][i]);
    } 
       
    first_total = first_idle + first_non_idle;
    second_total = second_idle + second_non_idle;

    float total_difference {second_total - first_total};
    float idle_difference {second_idle - first_idle};

    consumption = (total_difference - idle_difference) / total_difference;     
  }  
  else if(cpu_data.size() == 2)
  {
    for(long unsigned int i=0; i<cpu_data[0].size(); ++i)
    {
        if(i==index_idle || i==index_wait)
        {
            first_idle += std::stof(cpu_data[0][i]);
            second_idle += std::stof(cpu_data[1][i]);
        }
        else
        {
            first_non_idle += std::stof(cpu_data[0][i]);
            second_non_idle += std::stof(cpu_data[1][i]);
        }
    }        

    first_total = first_idle + first_non_idle;
    second_total = second_idle + second_non_idle;

    float total_difference {second_total - first_total};
    float idle_difference {second_idle - first_idle};

    consumption = (total_difference - idle_difference) / total_difference;

    cpu_data.erase(cpu_data.begin());
  }
  return consumption; 
}