Definition of polyphase merge sort, possibly with links to more information and implementations. POLYPHASE MERGE SORTING — AN ADVANCED TECHNIQUE. R. L. Gilstad. Minneapolis-Honeywell Regulator Company. Electronic Data Processing. This article demonstrates one of the best known merge sorts, the polyphase merge. I make no sensational claims regarding the performance of this particular .
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The leftmost file at list head always contains the least number of runs. The PolySort class constructor requires a polyphase merge sort to an InternalSort object Listing 4the number of work files desired, and the size in bytes of the merge buffers. One solution is to cast the function merhe argument to fool qsort into thinking merg getting the proper type of comparison function. Suppose we have three tapes, T1, T2, T3 and an input polyphase merge sort on T1 that will produce 34 sortt.
These discussions usually assume the reader knows what to do when the size of the data set exceeds available polyphase merge sort, or may simply refer to more weighty tomes such as Knuth [ 1 ].
Polyphase merge sort – Wikipedia
If any input file has more than one run, polyphase merge sort another phase would be required. So far, the package has been tested on input files ranging from one word, up to 3 million randomly-generated “words” roughly 24 MB of fixed-length source data. For N less than 8 working files, a polyphase merge sort achieves a higher effective run count reduction factor by unevenly distributing sorted runs between N-1 working files polyhase in next polyphase merge sort.
I set out to design the sort by breaking the task into a number of major parts:.
Polyphase merge sort
Retrieved from ” https: In that case, the merge routine simply decrements the null run count for that file polyphase merge sort does not add it to the active list. The sort has no control over the actual contents of the source file submitted to it, templates or not. When object construction fails, the client routine polyphase merge sort delete the invalid object.
The number of runs decreases by a factor of 2 polyphase merge sort each iteration, such as 64, 32, 16, 8, 4, 2, 1. With 4 files, the first iteration creates runs of size 3 original runs, the second iteration 5 original runs, the third iteration 9 original runs and so on, following the Fibonacci like pattern, 1, 3, 5, 9, 17, 31, 57, Polyphase merge sort we take next run from each tape, merge these and write ,erge to a2.
A simple example polyphase merge sort sorf the package to sort a file of random long integers appears in Listing In all cases, the source file contained “words” one to seven bytes long made of randomly generated characters. One run is left on each input tape, and merging those runs together will make the sorted file.
If input data remains, the sort must polyphase merge sort a new sequence for the next level and continue until exhausting the source data. When a file reaches the end of each polyphase merge sort, it merg drops out of the active list. This will ultimately produce an input file that contains less than the expected number of runs.
Polyphase merge sort discussions of sorting found polyphase merge sort programming literature center on internal array sorting. Any remaining dummy runs, when added to the actual number of runs generated, still preserve the ideal. The sort arranges the number of runs in each of the work files so that one becomes empty at the completion of each merge pass.
When this is done, we rewind all the tapes. This is done by extending basic 2-way merge to a k-way merge. The routine will ignore that file during the mini-pass. Bitonic sorter Batcher odd—even mergesort Pairwise sorting network.
As critical as this may polyphase merge sort though, the merge routine covers its tracks by following a “merge until empty” strategy when reading input files.
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Once attached, a Polyphase merge sort won’t delete or modify the source file in any way. Polyphase merge sort is faster for less than 8 tapes, while balanced merge sort is faster for 8 or more tapes. For our purpose, however, the polyphase sort must compute the osrt number of runs required for each work file at each level.
All of this is in keeping with an encapsulated class design. This is potentially a time-consuming procedure, especially for large source files. Replacement Selection Replacement section is a technique for producing runs. At the end of the iteration, one input file will polyphase merge sort been completely consumed and will polyphase merge sort the output file for the next iteration. For everything to work out optimally, the last merge phase should have exactly one run on each input file.