Browse Prior Art Database

Disk Algorithm

IP.com Disclosure Number: IPCOM000077676D
Original Publication Date: 1972-Sep-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 23K

Publishing Venue

IBM

Related People

Wallenbourg, JC: AUTHOR

Abstract

In connection with sorting, a special disk algorithm with the following properties has been suggested.

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Disk Algorithm

In connection with sorting, a special disk algorithm with the following properties has been suggested.

In phase 1, the distribution of strings is sequential using a logical track concept. The first string is written beginning on the first physical track on the first work area, then the first track on the second work area is used, etc. The second physical track on the first work area will be used after the first physical track on the N:th work area. A logical track can be said to contain up to N physical tracks, one from each work area.

At the end-of-phase, the physical areas will be divided into logical areas:

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Logical area M is the space that is empty. None of the other logical areas may be larger than logical area M. The logical areas must be sorted in size order.

In phase 2, the algorithm will be as in the balanced disk distribution algorithm, but using the logical areas instead. The first merge will be from logical area M-1 to logical area M, the second from area M-2 to area M-1, etc. At end-of-pass, other divisions of the logical areas can be done if considered optimal. Partial pass is possible anytime during phase 2.

In phase 3, the final merge will be done from the logical areas in a similar way to the balanced disk distribution algorithm.

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