Andreas Bauer, Viorica Botea, Mark Brown, Matt Gray, Daniel Harabor & John Slaney

CP 2010, 522—536

Presented by Heath Roehr

The G12 Platform Zinc: Constraint Modeling Language

The G12 IDE Modeling Layer: Meet-Pass Scenario Solving Layer Visualization Layer

Debugging with the G12 IDE Conclusion & Questions

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• Software platform for solving large-scale combinatorial optimization problems

• Supports • Linear & mixed integer programming• Constraint propagation & inference ┼ A variety of other search & inference

techniques for solving complex problems

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• Zinc is a first-order functional language with simple, declarative semantics

• Modeling languages separate the constraint model from the constraint program

• It provides• Mathematical notation-like syntax

• Expressive constraints (finite domain and integer, set and linear arithmetic)

• Separation of data from model

• High-level data structures and data encapsulation including constrained types

• User defined functions and constraints

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•SolvingThe problems are computationally challenging

•Debugging?Remember your homework...

•Conceptualizing & improving searchStaring at code is not really the smartest strategy

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Write constraint models in the input languages of G12 (Zinc & MiniZinc)

• Vector-oriented drawing tool • Associated script editor to

build custom animations

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MEET-PASS SCENARIO• Five sectors of railway track, S1,

. . . S5, are linearly connected• There is a siding accessible

from S3 big enough to hold one train

• Initially, there are trains in sectors S1, S2 and S4

S1 S2

S3 S4 S5

• The safety rules are that • No two trains may be in the

same sector at the same time• No train may enter a sector

occupied by another train, even if that other train is about to move on

• Trains may only move to adjacent sectors, of course

Constraints

Siding

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MEET-PASS SCENARIO

• Find the shortest plan that moves the train on S1 to S5 and returns the other two trains to their starting positions.

Initial

Goal

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Step 0

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 1

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 2

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 3

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 4

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 5

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 6

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 7

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 8

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 9

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 10

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 11

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 12

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 13

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 14

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 15

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 16

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 17

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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Step 18: Solution Found

MEET-PASS SCENARIO: A POSSIBLE SOLUTION

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ZINC EDITOR: MEET-PASS IMPLEMENTATION • Five sectors of railway

track, S1, . . . S5, are linearly connected

• There is a siding accessible from S3 big enough to hold one train• Initially, there are trains in sectors S1, S2 and S4• Move the train on S1 to S5 and return the other two trains to their starting positions.

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ZINC EDITOR: MEET-PASS IMPLEMENTATION

• Safety rules• Specific

implementation is outside the scope of this talk

• Assume they are accurate and valid

• Execute the search

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ZINC EDITOR: MEET-PASS IMPLEMENTATION

Variable Declaration

Constraints

Variable Definition

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ZINC EDITOR: SCREENSHOT

Syntax highlighting

Project-based code management

Outline views

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VISUALIZATION EDITOR

• Define arbitrary visualizations• Vector-based graphics editor• Script editor

• Scripting language• Any language that supports java

integration• Python• Lisp

• Default language is Lua• Lightweight• Portable• Suited for animation: used in video games

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VISUALIZATION EDITOR

Vector-based graphics editorGraphics properties editor

Project-based code management

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VISUALIZATION EDITOR• g12GetFromData(var)

• This method fetches the current contents of the decision variable var and makes its value available to the script.

• g12Draw(obj, props)• This method sets a list of properties, props, for object obj, where props may contain items such as the object’s positions on the canvas, color, opacity, scaling factor, etc.

Written in Java

Written in Lua

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The actual solver

Control the starting & stopping of the solving process

Collect detailed information about the solving process

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XML-based messaging

Separate Processes

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Build & display a constraint graphBuild & display a search tree

Render visualization based on custom animation script

Pre-defined visualizations

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Constraint Graph

Search Tree

Sample Pre-Defined Visualizations

Collapsed sub treeDomain split

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HOW IS DEBUGGING DIFFERENT IN THE G12 IDE?

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USER DEFINED BREAKPOINT VIEW

User defined breakpoints

“Search Events”(Events that induce the breakpoint)

The breakpoint “subscribes” to these search eventsEnable/disable breakpoints

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• Accomplished by • drawing objects• binding their animation to events that fire

during program execution

• Debugging is happening• At the conceptual level• Graphically: Domain-specific

CUSTOM VISUALIZATION AND ANIMATION

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“MEET-PASS” EXAMPLE

Propagation should deduce the position of the train…

Original formulation failed to deduce correctly, identifying an incorrect constraint model…

• IDEs tailored to CSP solving• ECLiPSE CLP

• Draw charts and graphs for solver output

• ILOG OPL Studio• Offers a search-tree view similar to that of the G12 IDE

• Choco• Java based visualizations from scratch

• Vector-based graphics processing programs• Most are more advanced than G12’s graphics

processor

• Using a custom visualization tool that is tightly integrated with debugging facilities is novel

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RELATED WORK

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• G12 IDE redefines the way users can interact with their solving CSPs

• Users• Can not only view classic CSP visualizations (such as

search tress)• They can also customize animations straight from

the IDE• G12 IDE Allows users to

• Update their constraint definitions & solver logic on the fly

• Based on feedback from the event-driven debugger & real-time visualizations

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