Q. Show the Programmes for Parallel Systems?

Adding elements of an array using two processor    

 int sum, A[ n] ;  //shared variables                                                                                              

void main ( ){

                         int i ;

for (i=0; i

scanf ("%d",&A[i] );                                                                                                   

sum=0;                                                                                                                         

// now create process to be executed by processor P1                                                 

fork(1) add (A,n/2,n-1, sum); // process to add elements from index n/2 to -

1.sum is output variable          // now create process to be executed by processor

P0                                                                                           add (A,0,n/2-1,

sum);                                                                                                                             

join 1 ;                                                                                                                          

printf ("%d", sum); 

}                             

add (int A[ ], int lower, int upper, int sum)

{

int sum1=0, i;                   

for (i=lower; i<=upper; i++)                  

sum1=sum1+A[i];                                  

lock sum;                                                

sum=sum+sum1;                                    

unlock  sum ;                                         

}                              

In this program last half of array is passed to processor P1 that adds them. For the meantime processor P₀ adds the first half of array. The variable sum is locked to avoid inconsistency.