dotprod_serial.c

/* 
* 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: 01/29/09 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()
{

  /* 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;

}

/*
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);
}