Complex sentence: A simple merge algorithm is then run left to right or right to left depending on which run is smaller, on the temporary memory and original memory of the larger run, the final sorted run being stored in the original memory of the two initial runs.
Split into simpler sentences: A simple merge algorithm runs left to right or right to left depending on which run is smaller, on the temporary memory and original memory of the larger run. The final sorted run is stored in the original memory of the two initial runs.