CSC/ECE 517 Fall 2014/OSS E1467 rsv

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Expertiza - Refactoring LeaderBoard model

Introduction

Expertiza<ref name="expertiza>Expertiza http://wikis.lib.ncsu.edu/index.php/Expertiza</ref> is a web application available to both students and professors. The Expertiza project is a system to create reusable learning objects through peer review. Expertiza supports team projects and the submission of almost any document type, including URLs and wiki pages. Students can keep a track of their assignments, teammates and can conduct peer reviews on diverse topics and projects. It is an open source project developed on Ruby on Rails platform. More information on Expertiza can be found here. The source code can be forked and cloned for making modifications.

As a part of the coursework of Object Oriented Design and Development, we were expected to refactor the funtionality of some modules of Expertiza. This wiki provides an insight into our contributions to the Open Source Software project 'Expertiza' by Refactoring the Users Controller.

Project Description

Classes involved: leaderboard.rb and associated other model and controllers classes. What it does: This class gets all the assignments in the course and all the participants in a course or in an assignment. It also caches all the scores of the participants in various assignments. Its responsible for calculating top 3 individuals which is to be displayed as the leaderboard for the class and generates a metric which aggregates peer review scores for all course assignments and then sorts individuals. Also it has a personal leaderboard to see a personal aggregated score. What needs to be done: Refactor getParticipantEntriesInAssignmentList method. Its very complex (Complexity=142). Seperate out computation of CS entries(metric) and refactor it to be more modular and elegant. You can even come up with a better metric to calculate an aggregate score for all peer reviews, metareviews(if any), teammate review, etc. Assign more weights to programming assignments. You will need to refactor other dependent classes. Come up with an efficient way to search for participants based on assignment ids. Refactor score hash for personal achievements. (Method: extractPersonalAchievements). Seperate out method which will rank individual personal achievements. Refactor addEntryToCSHash according to your new metric method.


Existing Code

Leaderboard class gets all the assignments within all the courses taken by currently logged in user. It also fetches any independent assignments (not associated with any course), that the user has taken. leaderboard model has following 3 important methods: 1. getParticipantEntriesInAssignmentList(assignmentList) ○ This method is responsible for calculating the leaderboard of all the participants associated with assignments in given assignment list. 2. extractPersonalAchievements(csHash, courseIdList, userId) ○ This method is responsible for calculating personal aggregated score. It also calculates the ranking of currently logged in user against total users associated with the same set of courses as that of current user. 3. addEntryToCSHash(qtypeHash, qtype, userid, csEntry, courseid) ○ This method is called internally from Leaderboard.getParticipantEntriesInAssignmentList. ○ This method aggregates score of a user grouped by course id, further grouped by questionnaire type. In the OSS project, we have refactored these methods along with other smaller methods in Leaderboard.rb, Leaderboard_helper.rb. We have also refactored ambiguous variable and method names.


We have keenly focussed in reducing the database calls, loops and redundant storage and computation. We have refactored many files related to Leaderboard implementation leading to enhancement of overall complexity of the feature. Following are some of the changes that we think are sharing in readme file. For all the other changes, please visit our forked repository (https://github.com/sanjeevs/expertiza/tree/rails4)


Changes

1. Leaderboard.rb ○ Methods like getIndependantAssignments and getParticipantEntriesInCourses are refactored to reduce the database calls within loop. Database calls have huge impact on overall complexity of the code and performance of the software. ○ sortHash : This method modified the input hash. We refactored it to not alter the input hash object, but rather return a new deep copy of the updated hash object. ○ extractPersonalAchievements : This method is refactored to use only 1 database call unlike several within the loop in its prior implementation. We have also removed redundantcode computation and made the logic easier to understand. The overall complexity of this method is reduced from 72 to 35 *. ○ addEntryToCSHash : This method is refactored to reduce the redundant code. The new method name is addScoreToResultantHash. As mentioned earlier, this is called internally by getParticipantEntriesInAssignmentList. The complexity of this method is reduced from 67 to 39 *.

○ getParticipantEntriesInAssignmentList : This method was the most complex method in the class. The new refactored method name is getParticipantsScore. The method was refactored on various aspects like reducing database calls drastically, removing redundant code computation, redundant data storage in complex group of hashes and series of conditional statements. We would like to mention that previously, the method had 10 database calls within loop and 1 outside loop. After refactoring, the new method has just 1 database call within loop and 3 outside loops. Also, the overall code complexity is reduced from 142 to 64 *. ○ There was a requirement in the project, that we should come up with an efficient way to search for participants based on assignment ids. However, upon investigation, we found that scores stored in table ScoreCache, gives us revieweeId which is either participantId or teamId. Therefore, we have a method getAssignmentMapping, which creates a mapping of participant and team with corresponding assignment. This is very useful while computing leaderboard. 2. Leaderboard_helper.rb ○ userIsInstructor : This method was refactored to reduce multiple database calls. 4 database calls was replaced by single call. ○ studentInWhichCourses : This method was refactored to reduce multiple database calls and remove unnecessary loops. 1 database call outside and 1 within a loop was replaced by a single call. ○ getTop3Leaderboards : This method is a dead code, not called from anywhere, therefore, we have commented this for the moment. There are several other changes in the views and controller which deal with renaming of the methods and variables, adding proper comments etc and minor code refactoring. Please refer to our forked github repository to view those changes. Lastly, we would like to recommend the readers to test the leaderboard functionality by any user who has participated in several assignments, some of them which is associated with any course and there are other existing users who have participated in the same assignment. e.g. user480/password

  • Code complexity measurement is according to Code Climate
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