Drools Planner Chtijug 2010

Ch’ti JUG

Jboss Drools
&
Drools Planner

21 janvier 2010

Ch’ti JUG ● Editeur de logiciels exclusivement dédiés aux enseignes du
Retail

● Création en 1986

● 35 M€ de CA en 2008 (+20 %/an en moyenne depuis 5 ans)

● 34 % à l’International

● 5 sites en France dont le siège à Roubaix. (Paris, Belfort,

Antibes, Vannes)

● 5 filiales hors hexagone : Shanghai, Portugal, Espagne,
Tunisie, Pologne en cours

● Une expérience éprouvée dans 60 pays

Ch’ti JUG Effectifs : 430 collaborateurs dans le monde, 360 en France, 300 ressources
basées à Roubaix

10
0 Experts Metiers

90 Directeur de Projet

80 C de Projet Métier
hef
70
C de Projet
hef
60 Techniques
Formateur et @learning
50
Directeursde Produits
40
30 Développeurs

20 Recette et Qualification

10 H L
ot ine

0 Préparateurset
Effectifs déploiem ents
4

Ch’ti JUG
Storeland pilote l’ensemble de votre supply chain étendue

Ch’ti JUG CYLANDE partenaire de la FFJ

Le judo véhicule des valeurs

Cylande a accompagné l’équipe de France
de Judo à Pékin

Ch’ti JUG

Une croissance résolument tournée vers l’international
Lauréat du Prix PME France CHINE ACFCI / CCIFC

Ch’ti JUG

Automated planning
with Drools Planner
Geoffrey De Smet
Drools Planner lead

"Do more with less."

Ch’ti JUG Agenda
 Use cases of automated planning
• N queens
• Bin packaging
• Employee shift rostering
• Examination timetabling
 Find the best solution
• With Drools Planner
 Calculate the score of a solution
• With Drools

Ch’ti JUG N Queens: use case
 Place n queens on a n-sized chess board
 No 2 queens can attack each other

Ch’ti JUG N queens: partially solved
 Score -1 for every 2 queens that can attack
each other

Score = -2

Ch’ti JUG N queens: an optimal solution

Score = 0

Ch’ti JUG N queens: demo
 Not optimized!
• Hello world example
 Not a real
planning problem
• I can make an
optimal solution
for any n queens
without a computer
• See Wikipedia

Ch’ti JUG NP complete
 Yellow item goes in first (or last)
• Why?
• Not the largest size
• Not the largest side
• So why?
 NP complete
• A given solution can be verified fast
• No efficient way to find a solution
• Is there even a solution?

Ch’ti JUG Real world bin packaging
 Not just 5 items
• 1000+ items
 Not just 1 container
• 100+ containers
• Different container types
 More constraints...
• Distribute weight evenly
• Not all fireworks in the same container
• ...

Ch’ti JUG Hard constraints
 Hard constraints must be fulfilled
 For example:
• Ensure continuous service
• At least 1 emergency nurse at any given time
• Labor laws
• Every 24 hours: at least 11 hours rest
• Every 7 days: at least 35 hours rest
• No shifts during approved vacation

Ch’ti JUG Soft constraints
 Soft constraints should be fulfilled as much
as possible
• Only after the hard constraints are fulfilled
 Each soft constraint is weighted
 For example:
• Fair night work assignment: weight 5
• Forward rotation: weight 10
• Nurse preferences: weight 1
• Ann dislikes Saturday night shifts
• Beth dislikes Wednesday afternoon shifts

Ch’ti JUG Hard and soft score
 Solution A B C
 Hard constraints
• 11 hours rest 1 0 0
 Soft constraints
• Fair night work
assignment 0 1000 1
• Weight 5
• Nurse preferences 0 0 4000
• Weight 1
 Total score -1H/0S 0H/-5000S 0H/-4005S
• A<B<C
• C is the best solution

Ch’ti JUG Hard constraints
 Exam conflict: 2 exams that share students should not occur in the
same period.
 Room capacity: A room's seating capacity should suffice at all times.
 Period duration: A period's duration should suffice for all of its
exams.
 Period related hard constraints should be fulfilled:
• Coincidence: 2 exams should use the same period (but possibly
another room).
• Exclusion: 2 exams should not use the same period.
• After: 1 exam should occur in a period after another exam's
period.
 Room related hard constraints should be fulfilled:
• Exclusive: 1 exam should not have to share its room with any
other exam.

Ch’ti JUG Soft constraints
 2 exams in a row.
 2 exams in a day.
 Period spread: 2 exams that share students
should be a number of periods apart.
 Mixed durations: 2 exams that share a room
should not have different durations.
 Front load: Large exams should be scheduled
earlier in the schedule.
 Period penalty: Some periods have a penalty when used.
 Room penalty: Some rooms have a penalty when used.

Ch’ti JUG Examination demo
 International timetabling
competition 2007
• Finished 4th (back then)
 7 minutes
• CPU depended
 Real word test data
 14 constraints
• 7 hard constraints
• 7 soft constraints

Ch’ti JUG Other use cases
 Vehicle routing
• Freight routing
 Scheduling
• Course, meeting, conference scheduling
• Appointment and resource scheduling
• Sport scheduling
 Storage organizing
 Machine queue planning
 ...

Ch’ti JUG Why use Drools Planner?
 Open source
• ASL (business-friendly)
 Maven-ready (JBoss repository)
 Documentation
• Reference manual
• Examples
 JBoss Drools community support
• User mailing list, issue tracking, …
• Blog & twitter (#droolsplanner)

Ch’ti JUG
Brute force
for (periodOfExam1 : periodList) {
exam1.setPeriod(periodOfExam1);
for (roomOfExam1 : roomList) {
exam1.setRoom(roomOfExam1);

for (roomOfExam2 : roomList) {
exam2.setRoom(roomOfExam2);
...
for (periodOfExamN : periodList) {
examN.setPeriod(periodOfExamN);
for (roomOfExamN : roomList) {
examN.setRoom(roomOfExamN);

Score score = calculateScore(solution);
cloneIfScoreIsBetter(solution, score);

} } } }…} }

Ch’ti JUG Needle in a haystack
 How many possible
solutions?
• 1096 exams
• 80 periods
• 28 rooms
 > habitants in Lille per km²?
• 6 483 hab./km²
Source: wikipedia

solutions?
• 1096 exams
• 80 periods
• 28 rooms
 > humans?
• 7.000.000.000 humans
Source: NASA (wikipedia)

solutions?
• 1096 exams
• 80 periods
• 28 rooms
 > minimum atoms in the
observable universe?
• 10^80 atoms
Source: NASA and ESA (wikipedia)

solutions?
• 1096 exams
• 80 periods
• 28 rooms
 > atoms in the universe
if every atom is a universe of
atoms?
• (10^80)^80 = 10^6400
Source: NASA and ESA (wikipedia)

Ch’ti JUG Do the math
 1 exam
• 80 periods and 28 rooms
• 80 * 28 = 2240 ways to schedule 1 exam
 2 exams
• 2240 * 2240 = 5.017.600
 3 exams
• 2240 * 2240 * 2240 = 11.239.424.000
 1096 exams
• 2240 * 2240 * … * 2240
• 2240^1096 = a little over 10^3671

Ch’ti JUG
A little over
10^3671
 744437246744648820113833159531546214974276974551140513162882691
3469284310834499031050210214743407656244813085240442809855321
17872268184924364558999914849676314196976841658179857396613906
3492625485909685725897730184010924994541828672670138943325039
683048943713412274829614721695599636159777727101713768378004615
48701272177587402234891701308937790853816473943603349353332893
68078384002213161233225755719910067066354676237665251240673552
3153767499024677368278799816044299431500884240408977216982760
67946148250230917492054728443158872165054373936157659332956136
774730870081258025518405492389480888615900164269035398348299
0003805674675524102808572658937105740571173904119233244862828
53392817922617168734507604739703552080299261320457186755798353
7967203299588154666629888459837384660489020381221523812268702
28697167564520947170314014038670253281783219898668392349799158
35407169443312860837423115961300328664844607892218572759207572
4811

Ch’ti JUG
A little over
10^3671
 604813577241247185462510563049535812195201797417621522126155060
76944992828720005800729579185467968191720128852327413111071565
0043989565813921764252807306941995041630327604298194478260407
65201495454290825675151996355311686689270103635691882586316830
6139401723974701085877081645821563181943787272983111911411368916
8267734458648249288525981253268712682909721892541332433788104
618254995718184937280503163787574781545179918774455713682720486
0856763230803748948170736540773077834904096264467405007381183
921101733071148798313412153048340998159011667296994070172526454
17836852601401021510814954906747082633216854492531462935276329
8262882437094345239245616252628477471654331980909505146422698
5500820819509960070516675580035694278266373295312687962113803
354280700964987221060506159614496708252300794687287842958627
4134471258439206305573503782097081716925686154420223798946020
9728873590430061008523877953514829733076235819258465550027938
41

Ch’ti JUG
A little over
10^3671
 41281947539904670755491533163612447621027075998378388100740372
5028189106738399600287059413396296063538199837169373556801830
5836646411561304836723541726522661983307438198684385880446218
050094809565635384648937983793088308243838089365451116083129
64868056598674131595193654957707706822143338172833633019666638
035983430262037019665125647894212392790462389810030266845803
0790315153020620193795388869486770234724354626457650058047468
161664023993402310021870051091820162111647624929917192405039351
1639247398607555167937946055347704746052684593317642558493208
66378895400041597447191732266335485557327003619802076964131266
186551891831601623573904848347851683860381473416171492241589945
908191501085456952341588756767389366458777600000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
00000

Ch’ti JUG
A little over
10^3671
 0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
0000000000000000000000000000000000000000000000000000000
00000000

Ch’ti JUG
A little over
10^3671
 0000000000000000000000000000000000000000000000000
000000000000000000000000000

 The search space is big!
• Compare with WWW size
• 22 020 000 000 pages
 Each possible solution
• 1096+ exams scheduled into
• 80 periods
• 28 rooms
• Still need to calculate the score

Ch’ti JUG Throw hardware at it?
 If 10^9 scores calculated per ms
• Not possible today!
• 31.579.200.000 ms in 1 year
• < 10^11 ms in 1 year
• 10^9 * 10^11 scores per year
• = 10^20 scores per year
 How many years? 10^3671 / 10^20
• = 10^3651 years
 CPU 1000 times faster
• It becomes 10^3648 years

Ch’ti JUG A dose of reality
 Find the optimal solution?
• Of a real world planning problem?
 Not in our lifetimes!
 Who cares?
• Beat the human planner(s) (=easy)
• Spend less resources
• Save more money
• Save the environment
• Make more people happy
• Never ending competition

Ch’ti JUG Smarter brute force?
 Eliminate subtrees
• Branch and bound
• Still too many for loops
• Still takes forever

if (exam1.shareStudentWith(exam2)
&& periodOfExam1.equals(periodOfExam2)) {
continue; // bug: best solution might break a hard constraint
}
...

Ch’ti JUG
Imperfect algorithms
(mimic a human)
 Deterministic
• First in, first assigned, never changed
• Easy to implement
• Drools Planner score support
• Fixed time (for example 18 seconds)
 Metaheuristic
• Move things around
• Start from result of deterministic algorithm
• Drools Planner implementations
• More time = better score

Ch’ti JUG Deterministic: N queens
 Demo
 Not feasible
• Not optimal
 Good initialization
• Jump 10 meter into the pool

Ch’ti JUG Deterministic: examination
List<Exam> sortedExamList = sortExamsOnDifficulty(examList);
for (exam : sortedExamList) {
// Determine best remaining spot
Score bestScoreOfExam = - INFINITY;
for (period : periodList) {
exam.setPeriod(period);
for (room : roomList) {
exam.setRoom(room);

Score score = calculateScore(solution);
if (score > bestScoreOfExam) {
bestScoreOfExam = score;
... store bestPeriod, bestRoom
}
}
}
… assign exam to bestPeriod, bestRoom
}

Ch’ti JUG Metaheuristic algorithms
 Local search: 1st, 2nd, 3rd and 4th in ITC 2007
• Simple local search (Hill climbing)
• Tabu search
• Local search ++
• Simulated annealing
• Great deluge
• ...
 Genetic algorithms: 5th in ITC 2007
 Ant colony optimization
 ...

Ch’ti JUG Move things around
 Move = from solution A to solution B
• Change the row of 1 queen

• Give 2 queens each others rows
• ...

Ch’ti JUG All moves from one solution
 Number of moves < number of solutions
• N queens
• n*n < n^n
• 4 queens
• 16 < 256
• 8 queens
• 64 < 16777216
• 64 queens
• 4096 < 10^116

Ch’ti JUG Metaheuristic: local search

Ch’ti JUG Local optima
 1) Deterministic StartingSolutionInitializer
 2) Simple local search
 3) Stuck in local optimum!

Source: Wikipedia

Ch’ti JUG Tabu search = local search++
 Solution tabu (high tabu size)
• Been there, no need to go there again
 Move tabu (low tabu size)
• Done that recently, no need to do that again
 Property tabu (low tabu size)
• Changed that recently,
no need to change that again

Ch’ti JUG Drool planner configuration
<selector>
<selector>
<moveFactoryClass>...PeriodChangeMoveFactory</...>
<relativeSelection>0.002</relativeSelection>
</selector>
...
<selector>
<moveFactoryClass>...ExamSwitchMoveFactory</...>
<relativeSelection>0.002</relativeSelection>
</selector>
</selector>
<accepter>
<completeSolutionTabuSize>1000</completeSolutionTabuSize>
<completeMoveTabuSize>7</completeMoveTabuSize>
</accepter>
<forager>
<foragerType>MAX_SCORE_OF_ALL</foragerType>
</forager>

Ch’ti JUG Termination
 Synchronous (configured)
• Max timeMillis/seconds/minutes/hours spend
• Score attained
• Max step count
• Max unimproved step count
 Asynchronous (from another thread)
• planner.terminateEarly();

Ch’ti JUG Double time !=> double score
Examination test data 7

Soft
score

Time (hours:minutes)

Ch’ti JUG Benchmarker utility
 Battle of different planner configurations
• Different algorithms (tabu search, ...)
• Different moves
• Different settings
 On multiple datasets
 Results are ranked:
• Best one wins
 Coming soon:
• Graph: best score over time

Ch’ti JUG JAVA vs SQL vs DRL
for (q1 : queenList) {
for (q2 : queenList) {
if (q1.getId() < q2.getId() && q1.getY() == q2.getY()) {
...
}
}
}

select *
from Queen q1, Queen q2
where q1.id < q2.id and q1.y = q2.y;

rule "multipleQueensHorizontal"
when
$q1 : Queen($id : id, $y : y);
$q2 : Queen(id > $id, y == $y);

Ch’ti JUG N queens: score rule
when
$q2 : Queen(id > $id, y == $y);
then
insertLogical(new IntConstraintOccurrence(
"multipleQueensHorizontal",
ConstraintType.NEGATIVE_HARD, 1,
$q1, $q2));
end

Ch’ti JUG Score rule isolation
when
$q2 : Queen(id > $id, y == $y);
then ...
end
rule "multipleQueensAscendingDiagonal"
when
$q1 : Queen($id : id, $ascendingD : ascendingD);
$q2 : Queen(id > $id, ascendingD == $ascendingD);
then ...
end
rule "multipleQueensDescendingDiagonal"
when
$q1 : Queen($id : id, $descendingD : descendingD);
$q2 : Queen(id > $id, descendingD == $descendingD);
then ...
end

Ch’ti JUG Examination: period spread
 2 exams that share students should be a
number of periods apart
rule "periodSpread"
when
$iw : InstitutionalWeighting(periodSpreadPenality != 0);
// For any 2 conflicting exams in the same period ...
$topicConflict : TopicConflict($leftT : leftTopic, $rightT : rightTopic);
$leftExam : Exam(topic == $leftT, $leftPeriod : period);
$rightExam : Exam(topic == $rightT, $rightPeriod : period);
// … which are in within the periodSpread
eval(Math.abs($leftPeriod.getPeriodIndex()
- $rightPeriod.getPeriodIndex())
< ($iw.getPeriodSpreadLength() + 1));
then
insertLogical(new IntConstraintOccurrence(... NEGATIVE_SOFT,
$topicConflict.getStudentSize() * $iw.getPeriodSpreadPenality(),
$leftExam, $rightExam));
end

Ch’ti JUG Summary
 Drools Planner solves planning problems
 Adding constraints is easy and scalable
 Switching/combining algorithms is easy

Ch’ti JUG
Q&A
 Home page
• http://www.jboss.org/drools/drools-planner.html
 Reference manual
• http://www.jboss.org/drools/documentation.html
 Blog
• http://blog.athico.com/search/label/planner
 Twitter
• #droolsplanner

64

Ch’ti JUG
Thanks for your attention!
 Home page
• http://www.jboss.org/drools/drools-planner.html
 Reference manual
• http://www.jboss.org/drools/documentation.html
 Blog
• http://blog.athico.com/search/label/planner
 Twitter
• #droolsplanner

65

Ch’ti JUG Licence
 Les photos et logos appartiennent à leurs
auteurs respectifs
 Le contenu de la présentation est sous
licence Creative Commons 2.0 France
• Contrat Paternité
• Pas d'Utilisation Commerciale
• Partage des Conditions Initiales à l'Identique
 http://creativecommons.org/licenses/by-nc-sa/2.0/fr/

Ch’ti JUG Cocktail

 Merci pour votre attention
 Merci à Cylande pour son sponsoring

Drools Planner Chtijug 2010

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