Heikki Linnakangas <hlinnaka(at)iki(dot)fi> writes: > The beauty of the polyphase merge algorithm is that it allows reusing > input tapes as output tapes efficiently ... So the whole idea of trying to > efficiently reuse input tapes as output tapes is pointless.
It's been awhile since I looked at that code, but I'm quite certain that it *never* thought it was dealing with actual tapes. Rather, the point of sticking with polyphase merge was that it allowed efficient incremental re-use of temporary disk files, so that the maximum on-disk footprint was only about equal to the volume of data to be sorted, rather than being a multiple of that. Have we thrown that property away?