Re: Replacement Selection

<mac_man2005(at)hotmail(dot)it> writes:
> Anyway, even in my RS implementation a longer run is created. The first M
> initialization elements will surely form part of the current run. M is the
> memory size so at least a run sized M will be created. After initialization,
> the elements are not suddenly output, but an element from heap is output
> into run as soon as I get an element from stream. In other words, for each
> element from stream, the root element of the heap is output, and the input
> element takes the root place into the heap. If that element is a "good
> record" I just heapify (since the element will be placed at the now free
> root place). If that input element is a dead record I swap it with the last
> leaf and reduce the heap size.

AFAICS that produces runs that are *exactly* the same length as Knuth's
method --- you're just using a different technique for detecting when
the run is over, to wit "record is not in heap" vs "record is in heap
but with a higher run number". I guess you would save some comparisons
while the heap is shrinking, but it's not at all clear that you'd save
more than what it will cost you to re-heapify all the dead records once
the run is over.

regards, tom lane