n - number of values
arr1 - array of integers to be sorted, modified on output
arr2 - array of integers to be reordered, modified on output
The arrays CANNOT overlap.
This function serves as an alternative to PetscSortIntWithArray(). While this function works for any array of integers it is significantly faster if the array is not totally random. There are exceptions to this and so it is highly recommended that the user benchmark their code to see which routine is fastest.