Logarithmic time cost optimal parallel sorting is not yet fast in practice

It is pointed out that, when looking for new and faster parallel sorting algorithms for use in massively parallel systems it is tempting to investigate promising alternatives from the large body of research done on parallel sorting in the field of theoretical computer science. It is shown how this kind of investigation can be done on a simple but versatile environment for programming and measuring of PRAM (parallel random access machine) algorithms. The practical value of Cole´s parallel merge sort algorithm has been investigated by comparing it with Batcher´s bitonic sorting. The O(log n) time consumption of Code´s algorithm implies that it must be faster than bitonic sorting which is o(log² n) time, if n is large enough. However, it has been found that bitonic sorting is faster as long as n is less than 1.2×10²¹ . Consequently, it is concluded that Cole´s logarithmic time algorithm is not fast in practice