Skip to main content
UploadLanguage (EN)Support
BusinessMobileSocial MediaMarketingTechnologyArt & PhotosCareerDesignEducationPresentations & Public SpeakingGovernment & NonprofitHealthcareInternetLawLeadership & ManagementAutomotiveEngineeringSoftwareRecruiting & HRRetailSalesServicesScienceSmall Business & EntrepreneurshipFoodEnvironmentEconomy & FinanceData & AnalyticsInvestor RelationsSportsSpiritualNews & PoliticsTravelSelf ImprovementReal EstateEntertainment & HumorHealth & MedicineDevices & HardwareLifestyle
Uploaded byTech_MX
PPTX, PDF11,630 views

Merging files (Data Structure)

This document discusses different techniques for merging files in revision control systems. It begins by introducing the concept of merging as reconciling multiple changes made to files. It then discusses external sorting techniques that can handle large amounts of data. The main merging techniques covered are two-way merging, three-way merging, and k-way merging. Two-way merging considers differences between two files alone, while three-way merging also looks at the original parent file. Three-way merging is generally more reliable with less need for user intervention. K-way merging uses a tournament sort algorithm to merge an arbitrary number of files.

Education◦Technology◦
Downloaded 158 times
MERGING FILES
INTRODUCTION  Merging in revision control, is a fundamental operation that reconciles multiple changes made to a revision-controlled collection of files.  Most often, it is necessary when a file is modified by two people on two different computers at the same time.  When two branches are merged, the result is a single collection of files that contains both sets of changes.  External sorting may be used.
EXTERNAL SORTING  External sorting is a term for a class of sorting algorithms that can handle massive amounts of data.  External sorting is required when the data being sorted do not fit into the main memory of a computing device and instead they must reside in the slower external memory.  External sorting typically uses a sort-merge strategy.  In the merge phase, the sorted sub files are combined into a single larger file.
MERGE TECHNIQUES  Two Way Merge  Three Way Merge  K-Way Merge
TWO WAY MERGE  A two-way merge performs an automated difference analysis between a file 'A' and a file 'B'.  This method considers the differences between the two files alone to conduct the merge and makes a "best- guess" analysis to generate the resulting merge.
TWO WAY MERGE
ALGORITHM
DISADVANTAGE OF TWO WAY MERGE  This type of merge is usually the most error prone.  Requires user intervention to verify and sometimes correct the result of the merge.
THREE WAY MERGE  A three-way merge is performed after an automated difference analysis between a file 'A' and a file 'B' while also considering the origin, or parent, of both files.  This type of merge is more likely to be usable in revision control systems, which can guarantee that such a parent exists and is known.  The merge tool examines the differences and patterns appearing in the changes between both files as well as the parent.
THREE WAY MERGE
ADVANTAGES OF THREE WAY MERGE  This merge is the most reliable and has performed well in practice.  It has also required the least amount of user intervention.  In many cases, requiring no intervention at all making the process eligible for task automation.
K-WAY MERGE ALGORITHM Let there be two arrays: •An array of k lists and •An array of k index values corresponding to the current element in each of the k lists, respectively. Main loop of the K-Way Merge algorithm: •Find the index of the minimum current item, minItem •Process minItem(output it to the output list) •For i=0 until i=k-1 (in increments of 1) If the current item of list i is equal to minItem then advance list i. •Go back to the first step.
K-WAY MERGE  Tournament sort is used.
PERFORMANCE FACTORS  The number of records to be sorted.  The size of the records.  The number of storage devices used.  The distribution of those devices on the available I/O channels.  The distribution of key values in the input files.
THANK YOU