source: CIVL/examples/pthread/CDAC/pthread-loop-carried.c@ 397ae5f

/***************************************************************************
                  C-DAC Tech Workshop : hyPACK-2013
                         October 15-18,2013 
 
  Example     : pthread-loop-carried.c
  
  Objective   : Restructuring Loop-carried dependence to Loop-
                independent dependence using pthread APIs
 
  Input       : Nothing.
 
  Output      : Time in Second for Serial And Parallel Execution.
                                                                                                                         
  Created     : MAY-2013   
 
  E-mail      : hpcfte@cdac.in     
                                     
****************************************************************************/
 
/*Header files inclusion */
 
#include<pthread.h>
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
 
/* define size of thread and number of thread */
#define N 100000000
#define numThread 4
    /* defining global variable */
    const double up = 1.0;
    double Sn = 1.0,origSn=1.0,Snp;
    double opts[N+1];
    double optp[N+1];
    int dist;
    pthread_mutex_t  mutex = PTHREAD_MUTEX_INITIALIZER;
 
/*call back function for thread */
 
void * dowork(int  threadid)
{
    int n;
    double Snpl;
    /* logic for parallized the code using pow() function */
    for(n=(threadid * dist) + 1 ; n<=((threadid +1) * dist); n++)
    {
            if(n==((threadid * dist)+1))
            {
                Snpl = origSn * pow(up,n);
            }
            else
            {
                Snpl = Snpl * up;
            }
            optp[n] = Snpl;
    }
     
    if(threadid == (numThread - 1))
    {
        Snp=Snpl;
    }
 
  
}
/* main () starts */
int main(int  argc, char * argv [])
{
 
    /*variable declaration */
    int n,t,status;
    pthread_t threads[numThread];
    pthread_attr_t pta;
    int ret_count;
    double time_start, time_end;
    struct timeval tv;
    printf("\n\t\t---------------------------------------------------------------------------");
        printf("\n\t\t Centre for Development of Advanced Computing (C-DAC)");
        printf("\n\t\t Email : hpcfte@cdac.in");
        printf("\n\t\t---------------------------------------------------------------------------");
    printf("\n\t\t Objective : Write pthread code to illustrate restructuring Loop-carried dependence to Loop-independent   dependence using pthread APIs.  \n ");
        printf("\n\t\t..........................................................................\n");
 
 
    if ( numThread > 8 )
    {
        printf("\n Number of thread should be less than or equal to 8 \n");
        return;
    }
 
    /*Taking start time for serial calculation */
    gettimeofday(&tv,NULL);
    time_start = (double)tv.tv_sec + (double)tv.tv_usec / 1000000.0;
     
    /* serial loop with loop carried Dependence */
    for (n=0 ; n<=N; ++n)
    {
        opts[n] = Sn;
        Sn = Sn * up;
    }
    /*Taking end time for serial calculation */
    gettimeofday(&tv,NULL);
    time_end = (double)tv.tv_sec + (double)tv.tv_usec / 1000000.0;
    printf("\n\t\t Time in serial Execution in  Seconds (T)  :  %lf",(time_end - time_start));
 
    dist = N/numThread;
    optp[0]= origSn;
    ret_count=pthread_attr_init(&pta);
 
    /*Taking start time for parallel calculation */
    gettimeofday(&tv,NULL);
        time_start = (double)tv.tv_sec + (double)tv.tv_usec / 1000000.0;
     
    /* Loop for Ceating Thread's */
    for(t=0;t<numThread;t++)
    {
        ret_count = pthread_create(&threads[t], &pta,(void *(*) (void *))  dowork, (void *)t);
            if (ret_count)
            {
               printf("ERROR; return code from pthread_create() is %d\n", ret_count);
               exit(-1);
            }
 
    }
    /* Loop For Join Thread's */
    for(t=0;t<numThread;t++)
        {
                pthread_join(threads[t],(void**) & status);
 
        }
 
     
    Snp = Snp * up;
    /*Taking end time for parallel calculation */
    gettimeofday(&tv,NULL);
        time_end = (double)tv.tv_sec + (double)tv.tv_usec / 1000000.0;
    printf("\n\t\t Time in parallel Execution in  Seconds (T) : %lf",(time_end - time_start));
    printf("\n");
     
    /*Loop For Comparning The Result */
    for (n=0 ; n<=N; ++n)
        {
                
        if((float)opts[n] !=(float) optp[n])
                {
            printf("Result is not Same ");
            return;
        }
        }
 
 
        printf("\nserial Sn= %lf parallel Snp= %lf\n",Sn,Snp);
        if((float) Sn!=(float)Snp)
        {
            printf("Both Serial(Sn) and Parallel (Snp) Variable are  Not Same ");
        }
     
}