Benchmark.C

Go to the documentation of this file.

#include <sys/times.h>
#include <iostream>
#include <sstream>

// g++ -O -Wall -fPIC Benchmark.C -o Benchmark

// cast from float to double
//
/*



*/
void cast_cost(unsigned int nbloop = 100000u)
{
        // to do the casting
        double d, d1 = 10.01; float f, f1 = 10.01f; struct tms t0, t; 

        // just the loop
        times(&t0);     
        for (unsigned int i = 0u; i < nbloop; i++ ) {
                for (unsigned int j = 0u; j < nbloop; j++ ) {
                }       
        }
        times(&t);
        std::cout << "User " << float(t.tms_utime-t0.tms_utime)/sysconf(_SC_CLK_TCK)
             << " second, System " << float(t.tms_stime-t0.tms_stime)/sysconf(_SC_CLK_TCK)
             << " seconds" << std::endl;

                
        // no cast
        times(&t0);
        for (unsigned int i = 0u; i < nbloop; i++ ) {
                for (unsigned int j = 0u; j < nbloop; j++ ) {   
//                      d = d1;         
                        d = double(f1);
                }
        }
        times(&t);
        std::cout << "User " << float(t.tms_utime-t0.tms_utime)/sysconf(_SC_CLK_TCK)
             << " second, System " << float(t.tms_stime-t0.tms_stime)/sysconf(_SC_CLK_TCK)
             << " seconds" << std::endl;
             
        // cast 
        times(&t0);     
        for (unsigned int i = 0u; i < nbloop; i++ ) {
                for (unsigned int j = 0u; j < nbloop; j++ ) {           
                        d = d1;
//                      d = double(f1); 
                }               
        }
        times(&t);
        std::cout << "User " << float(t.tms_utime-t0.tms_utime)/sysconf(_SC_CLK_TCK)
             << " second, System " << float(t.tms_stime-t0.tms_stime)/sysconf(_SC_CLK_TCK)
             << " seconds" << std::endl;
}

// memcpy versus assignment
/*

*/
void memcpy_cost(unsigned int nbloop = 100000u)
{
        // to do the casting
        double d, d1 = 10.01; float f, f1 = 10.01f; struct tms t0, t; 
        
        // no cast
        times(&t0);
        for (unsigned int i = 0u; i < nbloop; i++ ) {
                for (unsigned int j = 0u; j < nbloop; j++ ) {   
//                      d = d1; 
                        memcpy(&d,&d1,8);
//                      d = double(f1);
                }
        }
        times(&t);
        std::cout << "User " << float(t.tms_utime-t0.tms_utime)/sysconf(_SC_CLK_TCK)
             << " second, System " << float(t.tms_stime-t0.tms_stime)/sysconf(_SC_CLK_TCK)
             << " seconds" << std::endl;
             
        return;
        
        // cast 
        times(&t0);     
        for (unsigned int i = 0u; i < nbloop; i++ ) {
                for (unsigned int j = 0u; j < nbloop; j++ ) {           
//                      d = d1;
                        memcpy(&d,&d1,8);       
//                      d = double(f1); 
                }               
        }
        times(&t);
        std::cout << "User " << float(t.tms_utime-t0.tms_utime)/sysconf(_SC_CLK_TCK)
             << " second, System " << float(t.tms_stime-t0.tms_stime)/sysconf(_SC_CLK_TCK)
             << " seconds" << std::endl;
}


int main(int argc, char **argv)
{
        const int nbtest = 2;
        if ( argc == 1 ) 
                std::cout << " Usage is : \n\t" 
                          << argv[0] << " i \n i being a integer from 1 to "<< nbtest << std::endl;
        
        int nwhat = 0; unsigned int number = 100000u;
        if ( argc > 1 ) {
                std::istringstream what(argv[1]); what >> nwhat;        
        }
        if ( argc > 2 ) {
                std::istringstream what(argv[2]); what >> number;
        }
                
        switch( nwhat ) {
                case 1:
                        cast_cost(number);
                        break;
                case 2:
                        memcpy_cost(number);
                        break;
                default:
                        std::cout << " Unknown test number " << nwhat << std::endl;     
        }
        
        return 0;
}