Randomize array in a function instead of in the send loop. This will allow us to get rid of the inner send loop and instead send all integers which belong to one node in a single large send.
- Fix major bugs in items_per_rank computation: The quotient was reversed. Also, the divisor needs to be substracted by 1.
- Don't put the items in the "correct" array position on the slaves. It doesn't matter where they are there because each one has the whole array for itself.
Fix major bug in item send loop
Send all items at once instead of having a single send for each one. Reduces line count and increases performance.