Constraint Systems Laboratory 11/26/2015Zhang: MS Project Defense1 OPRAM: An Online System for Assigning Capstone Course Students to Sponsored Projects.

Constraint Systems Laboratory

04/18/23 Zhang: MS Project Defense 1

OPRAM: An Online System for Assigning Capstone Course

Students to Sponsored Projects

Juedong Zhang

Acknowledgments: NSF Award RI-111795



Outline Introduction

• Background• Motivations• Contributions

Problem Modeling & Solving Methods System Implementation & Features Conclusions & Future Work



Background CSE Capstone Course

• An integral part of the undergraduate curriculum• Professional development opportunities

ParticipantsStudents, sponsors, CSE faculty, & iLab staff

Team formation



Motivations Team assignment is challenging

• Large class (CS + CE)• Various constraints

• Capacity limit for each project• Students’ preferences• Sponsors’ preferences

Constraint-based system for decision support• Automatic solver generates solutions upon request • Interactive solver maintains consistency for user• Visual support guides user to make good assignments



Contributions1. Modeled the task as a Constrained Optimization

Problem (COP) with three optimization criteria2. Designed a search algorithm that can generate the

optimal solution in a reasonable amount of time3. Developed an interactive solver that maintains

consistency while the user explores the search space 4. Created a web GUI interface that encapsulates both

solvers and provides an unified user experience5. Co-built an MySQL database for data persistence



Outline Introduction Problem Modeling & Solving Methods

• Problem modeling• Problem solving methods• Evaluation of search performance

System Implementation & Features Conclusions & Future Work



Modeling: COP Given

• Variables: The students enrolled in the Capstone Course• Domains: The projects applied to which a student applies• Hard constraints:

• A project’s capacity limit• A student does not choose a project or a sponsor does not

choose a student• Soft constraints: Students/sponsors preferences between 0…5• Objective function: Three criteria based on preferences

Query: find a value for each variable such that • All hard constraints are satisfied and • The objective function is optimized



Modeling: Soft Constraints Students preferences

“I am interested in working on this project.”

Sponsors preferences

“I think this student is a good fit for my project.”

Agreeableness of the statement

a preference score



Modeling: Combining Preferences

Product of preferences is more sensitive



Modeling: Objective Function Avg

• Maximize the average value over all preferences

Geo Avg• Maximize the geometric average value over all preferences

Maxmin• Maximize the minimum value over all preferences


Problem Solving Method Backtrack search Variable Ordering

• First choose the student with the least number of projects (i.e., least-domain first)

Value Ordering• Assign to a student first the project with the highest preference

(i.e., most promising value)

Constraint propagation by local consistency Exhaustive, depth-first search Branch-and-bound with a heuristic function



Local Consistency Node consistency

• Apply to the zero preference constraint• Remove the 0 value from the domain of every variable

Generalized arc consistency (GAC)• Apply to the capacity constraint• Remove the value (project) from the domain of all

future variables when the load of that project is reached


GAC is the foundation of our interactive solver


Heuristic Function h Given an assignment of i variables

• The cost of the partial solution

• The estimated cost of remaining assignments

• The total estimated cost

h(.)• Choose the value with highest preferences, even if values are

inconsistent with partial solution• h(.) is admissible, it never underestimates the cost of the real

solution



Search: FC-BnB search algorithm

Forward checking (FC) algorithm [Haralick and Elliott, 1980]

• A systematic search technique• After a variable is instantiated, it looks ahead (executes GAC)• When detecting a domain wipeout, it backtracks chronologically

Branch-and-Bound• Finds a first solution quickly, the incumbent• After a variable is instantiated, compares the quality of current

solution to that of the incumbent, updates incumbent• Exhaustive search, linear in space


FC- BnB is the foundation of our automatic solver


{(P2,5)}

{(P2,5), (P1,3)}

{(P3,3), (P1,1)}

Variable Domain

CurrentVariable

If Avg optimization criterion is used

f ((V1,5), (V2,5), (V3,3), (V4,5), (V5,5), (V6,))

= g ((V1,5), (V2,5)) + h ((V3,3), (V4,5), (V5,5), (V6,3))

= ((5 + 5) + (3 + 5 + 5 + 3)) / 6

= 4.33 Estimated solution quality at V2. Proceed to V3 only if it is better than incumbent

FutureVariables

V1 V2 V3 V4 V5 V6

(P2,5) (P2,5) (P3,3) (P1,5) (P3,5) (P1,3)

The h function ignores hard constraintsAssignments made by FCV1

V2

V3

V4

V5

V6

Illustrating Search: Example

{(P1,5), (P3,3)}

Projects removed by FC to comply with the capacity constraints

Six students V1 ~ V6

Three projects P1 ~ P3, each with a capacity of 2



Evaluating search: CPU

Data Sets• Fall 2013: 45 students, 11 projects• Spring 2014: 10 students, 3 projects

Impact of the h function



Evaluating Search: Solution Quality

Impact of the optimization criterion: comparing optimal solutions




Outline Introduction Problem Modeling & Solving Methods System Implementation & Features

• System architecture• iLab infrastructure• OPRAM architecture

• OPRAM Functionalities• Web GUI• The Legend’s color map• Interactive solver• Automatic solver• Solution comparison

Conclusions & Future Work


04/18/23 Zhang: MS Project defense 19

iLab Infrastructure

A user’s view

UserRegistration

InformationExchange

ProjectAssignment

Students / Sponsors

ProgressManagement

Instructors / iLab Staff

iLabAdministrator Module we developed

Module in progress


04/18/23 Zhang: MS Project defense 20

iLab Infrastructure

A system view

UserRegistration

InformationExchange

iLabDB

ProgressManagement

iLab Info Project

OPRAMProjectAssignment

iLab X Project

Module we developed

Module we co-developed

Module in progress


OPRAM Architecture

Google Web Toolkit


Server(Backend)

Client(GUI)

RPC

Google Web Toolkit Application

Java EE AJAX

Runs in Browser

Runs on Server


OPRAM Architecture

Remote Procedure Call (RPC)



OPRAM Architecture

Software design


RPC

GUIServiceClientImpl.Service

Async.

ServiceServiceServerImpl.

ClientServer

DBAccess

AutoSolver

InteractiveSolver

Request

Reply

Interface

ImplementationColor legend:


Web GUI



Legend’s Color Map



Interactive Solver: Student View


Project not available

Total number of students

1-semester or2-semester student

Preference


Interactive Solver: Project View


Project overview sub-panel Individual project sub-panel

Project not available

Total numberof projects

How manymore students

can be assignedAverage preference

Individual projecttab

Preference

Display the list of projects applied by the student when mouseover the preference

Project the student currently assigned to is shown in bold


Automatic Solver


Three options:10 seconds1 minute5 minutes


Solution Comparison


Only comparable solutions are displayed

Three additional metrics for current solution listed



Outline Introduction Problem Modeling & Solving

Methods System Implementation & Features Conclusions & Future Work


Conclusions Designed & implemented a web-base system

for Capstone Course project assignment decision support

OPRAM demonstrated significant improvements • on time to solution • as well as the quality of assignment found

CSE faculty and iLab staff are satisfied with OPRAM’s capabilities and have decided to take advantage of it in the upcoming semester



Future Work A formal proof for NP-hardness of this assignment

problem Explore other optimization criteria such as “stable

matching” Explore whether or not ‘a minimum size per project’ is

appropriate Support further interoperability between our two solvers Conduct longitudinal study of usefulness & flexibility




Thank you

I welcome your questions

Constraint Systems Laboratory 11/26/2015Zhang: MS Project Defense1 OPRAM: An Online System for Assigning Capstone Course Students to Sponsored Projects.

Documents

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preferences maxmin

studentssponsors preferences