PLINQ result is wrong and varies in different run

Question

I am learning PLINQ. I tried on example given on a site. However I can see that the result is wrong and also varies when I re-run the program many times. First it does not gives all prime numbers and second it gives only 9591 random prime numbers.

IEnumerable<int> numbers = Enumerable.Range (3, 100000-3);

var parallelQuery = 
  from n in numbers.AsParallel()
  where Enumerable.Range (2, (int) Math.Sqrt (n)).All (i => n % i > 0)
  select n;

int[] primes = parallelQuery.ToArray();

Appreciate any help!

Answer 1

There are 9592 prime numbers below 100,000, and your range does not include 2, which is a prime number.

The order of the prime numbers will vary, because you do not sort them, and have no control over how PLINQ splits the work into parallel chunks.