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Solving Problems with
Constraints
Karen E. Petrie
What is a Scientist?
What do you think a scientist does?
 Choose one task:



Draw a picture of a scientist;
Write a timetable for a scientist’s day
(a timetable sheet is provided)
What is a scientist?
I am a scientist.
 As are all the other adults in the room.
 What does it mean to be a scientist?
 What kind of work do we do?

What did you say you do?
 Mathematician
 I never could do maths
Computer science
 My son plays…
 Could you fix…
Artificial
Intelligence
So: What is AI?
“A singular consciousness that spawned an
entire race of machines”
Morpheus, The Matrix
“The scientific understanding of the
mechanisms underlying thought and intelligent
behaviour and their embodiment in machines."
AAAI
“Making computers do anything that they can
not currently do without human intervention”
Karen Petrie
It’s not all about robots?
You have
10 minutes!
A Puzzle

Place the numbers 1 through 8 in the
nodes such that:

Each number appears exactly once
– No connected
nodes have
consecutive
numbers
?
?
?
?
?
?
?
?
Modeling
Each node  a variable
 {1, …, 8}  values in the domain of each
variable
 No consecutive numbers  a constraint



(vi, vj)  |vi – vj| > 1
All values used  all-different constraint
Heuristic Search
{1, 2, 3, 4, 5, 6, 7, 8}
?
?
?
1?
8?
?
?
?
Inference/Propagation
{1, 2, 3, 4, 5, 6, 7, 8}
?
?
?
1?
8?
?
?
{1, 2, 3, 4, 5, 6, 7, 8}
?
Inference/Propagation
{3, 4, 5, 6}
4?
{3, 4, 5, 6}
6?
{3, 4, 5, 6, 7}
7?
{2, 3, 4, 5, 6}
1?
8?
3?
5?
{3, 4, 5, 6}
{3, 4, 5, 6}
2?
Research into Constraint Computation

Modelling


Heuristic Search


What should the variables/domains/constraints
be?
How should search progress?
Inference/Propagation

How much effort should be spent on inference?
More about CP

For the rest of the afternoon you can learn
more about CP by playing with the puzzles
at:


http://4c.ucc.ie/web/outreach
If you have any questions or are stuck, than
you can ask one of the `scientists’ for help!
Thanks for joining us
today!
www.4c.ucc.ie/web/outreach