Parallel quicksort openmp

[pitsianis]

I spawned a new thread, with the two codes in one, here:

@spawn large memory allocation reduced when some code abstracted out in a function

In another discussion, https://discourse.julialang.org/t/parallel-quicksort-openmp/88499 bizarre behavior that requires further attention and explanation came up. A recursive textbook implementation of quicksort makes no memory allocations as it modifies its argument input vector. However, the straightforward parallelization by @spawning the first recursive call results in a large number and volume of memory allocations. As a result, the parallel code is slower than the sequential. The above …

@gitboy16 or anybody else, please post there the mergesort with the opposite behavior.