dotprod_serial.c

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/******************************************************************************
* FILE: dotprod_serial.c
* DESCRIPTION:
*   This is a simple serial program which computes the dot product of two 
*   vectors.  The threaded version can is dotprod_mutex.c.
* SOURCE: Vijay Sonnad, IBM
* LAST REVISED: 04/05/05 Blaise Barney
******************************************************************************/
#include <stdio.h>
#include <stdlib.h>

/*   
The following structure contains the necessary information  
to allow the function "dotprod" to access its input data and 
place its output so that it can be accessed later. 
*/

typedef struct 
{
  double      *a;
  double      *b;
  double     sum; 
  int    veclen; 
} DOTDATA;

#define VECLEN 100
  DOTDATA dotstr; 

/*
We will use a function (dotprod) to perform the scalar product. 
All input to this routine is obtained through a structure of 
type DOTDATA and all output from this function is written into
this same structure.  While this is unnecessarily restrictive 
for a sequential program, it will turn out to be useful when
we modify the program to compute in parallel.
*/

void *dotprod(void)
{

/* Define and use local variables for convenience */

   int start, end, i; 
   double mysum, *x, *y;

   start=0;
   end = dotstr.veclen;
   x = dotstr.a;
   y = dotstr.b;

/*
Perform the dot product and assign result
to the appropriate variable in the structure. 
*/

   mysum = 0;
   for (i=start; i<end ; i++) 
    {
      mysum += (x[i] * y[i]);
    }
   dotstr.sum = mysum;

   return ;
}

/*
The main program initializes data and calls the dotprd() function.
Finally, it prints the result.
*/

int main (int argc, char *argv[])
{
int i,len;
double *a, *b;
   
/* Assign storage and initialize values */
len = VECLEN;
a = (double*) malloc (len*sizeof(double));
b = (double*) malloc (len*sizeof(double));
  
for (i=0; i<len; i++) {
  a[i]=1;
  b[i]=a[i];
  }

dotstr.veclen = len; 
dotstr.a = a; 
dotstr.b = b; 
dotstr.sum=0;

/* Perform the  dotproduct */
dotprod ();

/* Print result and release storage */ 
printf ("Sum =  %f \n", dotstr.sum);
free (a);
free (b);
}