How to Partition an Array
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Suppose the array is of size n
Suppose we have p processes, with id-s in [ 0, p )

Then process id should work on the range
  [ (id * n) / p, ((id + 1) * n) / p )

Example:

n = 11
p = 4

Thread 0	Thread 1	Thread 2	Thread 3
[0, 2) 		[2, 5) 		[5, 8) 		[8, 11)