Question

Consider the following problem Input: array of integers. Check, whether it is sorted in descending order How to solve this problem in parallel? Propose an algorithm Calculate its work, span and parallelism

Answer 1

#include<iostream>
#include<climits>
using namespace std;
int main()
{
int i,n;
cout<<"Enter size of array : ";
cin>>n;
int arr[n];
cout<<"Enter "<<n<<" elements : ";
for(i=0;i<n;i++)
cin>>arr[i];
int prev=INT_MAX;
for(i=0;i<n;i++)
{
if(arr[i]<prev)
{
prev=arr[i];
continue;
}
else
break;
}
if(i==n)
cout<<"Array is in descending order\n";
else
cout<<"Array not in descending order\n";
}

Enter size of array 5 Enter 5 elements 5 4 3 2 1 rray is in descending order Process returned θ (0x0) execution time : 8.585 s Press any key to continue.

/*Solution in parallelism, that is to check whether an array of integers are sorted in descending order or not

without storing the elements in array

*/

function main()

{

read n //where n denotes the size of the array

prev=MAX // prev is an integer variable which stores previous visited value of the input

for i=0 to n-1

read currentValue //val is an integer variable that stores current value of the input

if(currentValue<prev) //If previous value is greater than the current value then array is sorted upto this point

prev=currentValue //Update prev value to compare it with the next input

continue;

else

break;

//If the for loop iteration iterated n times

//then array is in descending order otherwise not

if(i==n)

print "Array is in descending order"

else

print "Array is not in descending order"

}

Parallelism:

Since the elements are not stored in a array it is evaluated for the task while taking input that is it is solved using parallelism.

Work:

Since the loop is iterating n times so the work span is O(n)