SlideShare a Scribd company logo
Carlo Lombardi,  June  2008 Theoretical  Computer  Science Primal-Dual Algorithms A brief survey of  Primal-Dual Algorithms  as an approximation technique  for optimization problems Scribe: Carlo Lombardi [email_address]
Carlo Lombardi,  June  2008 Theoretical  Computer  Science Overview ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]
Carlo Lombardi,  June  2008 Theoretical  Computer  Science Introduction ,[object Object],[object Object],[object Object]
Carlo Lombardi,  June  2008 Theoretical  Computer  Science Minimum Weighted Vertex Cover Vertex Cover Problem “ Each edge is covered by at least one node” + Weighted Verteces “ Each vertex has a weight” + Minimization of total weight “ Minimize the total weight” = Minimum Weighted Vertex Cover (WVC)
Carlo Lombardi,  June  2008 Theoretical  Computer  Science WVC: ILP and LP formulation We formulate the WVC as an Integer Linear Program (ILP) defining a variable  x i  for each vertex ( x i =1 if vertex i belongs to the cover, 0 otherwise).  ILP FORMULATION LP FORMULATION by relaxing integrality constraints
Carlo Lombardi,  June  2008 Theoretical  Computer  Science WVC: Rounding the LP solution Primal-Dual Method We need to  solve LP formulation …it can be expensive for  problems having many constraints!!! Can we do something clever?
Carlo Lombardi,  June  2008 Theoretical  Computer  Science A different approach to LP relaxations: Primal-Dual strategy Main idea: !!! Don’t solve LP totally !!! Obtain a feasible integral solution to the LP ( Primal)  from scratch using a related LP ( Dual ) to  guide your decision . LP Primal LP Dual Good approximated solution “ Solve me” “ I’ll be your guide”
Carlo Lombardi,  June  2008 Theoretical  Computer  Science P-D strategy: Background theoretic properties (1/2) PRIMAL DUAL (Weak Duality)  For any feasible Primal-Dual solution pair (x,y) : = if (x,y) is optimal (Strong Duality)  If either the Primal or Dual have bounded optimal solution, the both of them do. Moreover, their objective functions values are qual.  That is: (Complementary Slackness)  Let  (x,y)  be a solutions to a primal-dual pair of LPs with bounded optima. Then  x  and  y  are both optimal iff all of the following hold
Carlo Lombardi,  June  2008 Theoretical  Computer  Science P-D strategy: Background theoretic properties (2/2) (Weak Duality)  For any feasible Primal-Dual solution pair (x,y) : The dual solution is  a lover bound  for primal solution = if (x,y) is optimal (Strong Duality)  If either the Primal or Dual have bounded optimal solution, the both of them do. Moreover, their objective functions values are qual.  That is: At the optimum the evaluation of solutions coincides (Complementary Slackness)  Let  (x,y)  be a solutions to a primal-dual pair of LPs with bounded optima. Then  x  and  y  are both optimal iff all of the following hold Only If a dual constraints is tight the corresponding primal variables can be greater than 0 (it can participate to the primal solution)
Carlo Lombardi,  June  2008 Theoretical  Computer  Science Primal-Dual strategy
Carlo Lombardi,  June  2008 Theoretical  Computer  Science WVC : The D-P Algorithm ,[object Object],[object Object],[object Object],[object Object],[object Object],Primal Dual
Carlo Lombardi,  June  2008 Theoretical  Computer  Science Analysis of Program 2.7 (Weak Duality) Note that for every  it holds: (1) The o.f. is infact From the  (1) Because we are considering all vertices in V Each edge in E is taken two times
Carlo Lombardi,  June  2008 Theoretical  Computer  Science References ,[object Object],[object Object]

More Related Content

What's hot

aaoczc2252
aaoczc2252aaoczc2252
aaoczc2252
Perumal_Gopi42
 
Lecture 4 duality and sensitivity in lp
Lecture 4 duality and sensitivity in lpLecture 4 duality and sensitivity in lp
Lecture 4 duality and sensitivity in lp
kongara
 
Unit.3. duality and sensetivity analisis
Unit.3. duality and sensetivity analisisUnit.3. duality and sensetivity analisis
Unit.3. duality and sensetivity analisis
DagnaygebawGoshme
 
Duality in Linear Programming
Duality in Linear ProgrammingDuality in Linear Programming
Duality in Linear Programming
jyothimonc
 
Duality in Linear Programming Problem
Duality in Linear Programming ProblemDuality in Linear Programming Problem
Duality in Linear Programming Problem
RAVI PRASAD K.J.
 
Lesson 28
Lesson 28Lesson 28
Lesson 28
Avijit Kumar
 
Lesson 29
Lesson 29Lesson 29
Lesson 29
Avijit Kumar
 
Canonical form and Standard form of LPP
Canonical form and Standard form of LPPCanonical form and Standard form of LPP
Canonical form and Standard form of LPP
Sundar B N
 
5. advance topics in lp
5. advance topics in lp5. advance topics in lp
5. advance topics in lp
Hakeem-Ur- Rehman
 
Unit.4.integer programming
Unit.4.integer programmingUnit.4.integer programming
Unit.4.integer programming
DagnaygebawGoshme
 
Lesson 32
Lesson 32Lesson 32
Lesson 32
Avijit Kumar
 
Lesson 31
Lesson 31Lesson 31
Lesson 31
Avijit Kumar
 
Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...
Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...
Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...
IJERA Editor
 
LPP, Duality and Game Theory
LPP, Duality and Game TheoryLPP, Duality and Game Theory
LPP, Duality and Game Theory
Purnima Pandit
 
Numerical analysis simplex method 2
Numerical analysis  simplex method 2Numerical analysis  simplex method 2
Numerical analysis simplex method 2
SHAMJITH KM
 
Fuzzy Membership Function
Fuzzy Membership Function Fuzzy Membership Function
Paper id 252014152
Paper id 252014152Paper id 252014152
Paper id 252014152
IJRAT
 
Linear programming
Linear programmingLinear programming
Linear programming
Ishu Priya Agarwal
 
Integrated methods for optimization
Integrated methods for optimizationIntegrated methods for optimization
Integrated methods for optimization
Springer
 
Fuzzy report
Fuzzy reportFuzzy report
Fuzzy report
Rajanikanta Pradhan
 

What's hot (20)

aaoczc2252
aaoczc2252aaoczc2252
aaoczc2252
 
Lecture 4 duality and sensitivity in lp
Lecture 4 duality and sensitivity in lpLecture 4 duality and sensitivity in lp
Lecture 4 duality and sensitivity in lp
 
Unit.3. duality and sensetivity analisis
Unit.3. duality and sensetivity analisisUnit.3. duality and sensetivity analisis
Unit.3. duality and sensetivity analisis
 
Duality in Linear Programming
Duality in Linear ProgrammingDuality in Linear Programming
Duality in Linear Programming
 
Duality in Linear Programming Problem
Duality in Linear Programming ProblemDuality in Linear Programming Problem
Duality in Linear Programming Problem
 
Lesson 28
Lesson 28Lesson 28
Lesson 28
 
Lesson 29
Lesson 29Lesson 29
Lesson 29
 
Canonical form and Standard form of LPP
Canonical form and Standard form of LPPCanonical form and Standard form of LPP
Canonical form and Standard form of LPP
 
5. advance topics in lp
5. advance topics in lp5. advance topics in lp
5. advance topics in lp
 
Unit.4.integer programming
Unit.4.integer programmingUnit.4.integer programming
Unit.4.integer programming
 
Lesson 32
Lesson 32Lesson 32
Lesson 32
 
Lesson 31
Lesson 31Lesson 31
Lesson 31
 
Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...
Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...
Unsteady MHD Flow Past A Semi-Infinite Vertical Plate With Heat Source/ Sink:...
 
LPP, Duality and Game Theory
LPP, Duality and Game TheoryLPP, Duality and Game Theory
LPP, Duality and Game Theory
 
Numerical analysis simplex method 2
Numerical analysis  simplex method 2Numerical analysis  simplex method 2
Numerical analysis simplex method 2
 
Fuzzy Membership Function
Fuzzy Membership Function Fuzzy Membership Function
Fuzzy Membership Function
 
Paper id 252014152
Paper id 252014152Paper id 252014152
Paper id 252014152
 
Linear programming
Linear programmingLinear programming
Linear programming
 
Integrated methods for optimization
Integrated methods for optimizationIntegrated methods for optimization
Integrated methods for optimization
 
Fuzzy report
Fuzzy reportFuzzy report
Fuzzy report
 

Similar to Primal Dual

Primal Dual
Primal DualPrimal Dual
Primal Dual
carlol
 
Hardness of approximation
Hardness of approximationHardness of approximation
Hardness of approximation
carlol
 
P, NP, NP-Complete, and NP-Hard
P, NP, NP-Complete, and NP-HardP, NP, NP-Complete, and NP-Hard
P, NP, NP-Complete, and NP-Hard
Animesh Chaturvedi
 
Balaji-opt-lecture6-act.ppt
Balaji-opt-lecture6-act.pptBalaji-opt-lecture6-act.ppt
Balaji-opt-lecture6-act.ppt
JamesGreen666883
 
Balaji-opt-lecture5-linear program sp13.ppt
Balaji-opt-lecture5-linear program sp13.pptBalaji-opt-lecture5-linear program sp13.ppt
Balaji-opt-lecture5-linear program sp13.ppt
gokulkumaraguru8
 
Slides
SlidesSlides
Slides
xbj25kl
 
Algorithm chapter 10
Algorithm chapter 10Algorithm chapter 10
Algorithm chapter 10
chidabdu
 
UNIT -IV DAA.pdf
UNIT  -IV DAA.pdfUNIT  -IV DAA.pdf
UNIT -IV DAA.pdf
Arivukkarasu Dhanapal
 
Compositional Program Analysis using Max-SMT
Compositional Program Analysis using Max-SMTCompositional Program Analysis using Max-SMT
Compositional Program Analysis using Max-SMT
Facultad de Informática UCM
 
C&s sparse june_2010
C&s sparse june_2010C&s sparse june_2010
C&s sparse june_2010
mpbchina
 
Dynamic programming
Dynamic programmingDynamic programming
Dynamic programming
Jay Nagar
 
A Decomposition Technique For Solving Integer Programming Problems
A Decomposition Technique For Solving Integer Programming ProblemsA Decomposition Technique For Solving Integer Programming Problems
A Decomposition Technique For Solving Integer Programming Problems
Carrie Romero
 
A New Lagrangian Relaxation Approach To The Generalized Assignment Problem
A New Lagrangian Relaxation Approach To The Generalized Assignment ProblemA New Lagrangian Relaxation Approach To The Generalized Assignment Problem
A New Lagrangian Relaxation Approach To The Generalized Assignment Problem
Kim Daniels
 
Np
NpNp
7f44bdd880a385b7c1338293ea4183f930ea
7f44bdd880a385b7c1338293ea4183f930ea7f44bdd880a385b7c1338293ea4183f930ea
7f44bdd880a385b7c1338293ea4183f930ea
Alvaro
 
Probabilistic Abductive Logic Programming using Possible Worlds
Probabilistic Abductive Logic Programming using Possible WorldsProbabilistic Abductive Logic Programming using Possible Worlds
Probabilistic Abductive Logic Programming using Possible Worlds
Fulvio Rotella
 
NON LINEAR PROGRAMMING
NON LINEAR PROGRAMMING NON LINEAR PROGRAMMING
NON LINEAR PROGRAMMING
karishma gupta
 
Deep VI with_beta_likelihood
Deep VI with_beta_likelihoodDeep VI with_beta_likelihood
Deep VI with_beta_likelihood
Natan Katz
 
Introduction to Max-SAT and Max-SAT Evaluation
Introduction to Max-SAT and Max-SAT EvaluationIntroduction to Max-SAT and Max-SAT Evaluation
Introduction to Max-SAT and Max-SAT Evaluation
Masahiro Sakai
 
Analysis and Design of Algorithms notes
Analysis and Design of Algorithms  notesAnalysis and Design of Algorithms  notes
Analysis and Design of Algorithms notes
Prof. Dr. K. Adisesha
 

Similar to Primal Dual (20)

Primal Dual
Primal DualPrimal Dual
Primal Dual
 
Hardness of approximation
Hardness of approximationHardness of approximation
Hardness of approximation
 
P, NP, NP-Complete, and NP-Hard
P, NP, NP-Complete, and NP-HardP, NP, NP-Complete, and NP-Hard
P, NP, NP-Complete, and NP-Hard
 
Balaji-opt-lecture6-act.ppt
Balaji-opt-lecture6-act.pptBalaji-opt-lecture6-act.ppt
Balaji-opt-lecture6-act.ppt
 
Balaji-opt-lecture5-linear program sp13.ppt
Balaji-opt-lecture5-linear program sp13.pptBalaji-opt-lecture5-linear program sp13.ppt
Balaji-opt-lecture5-linear program sp13.ppt
 
Slides
SlidesSlides
Slides
 
Algorithm chapter 10
Algorithm chapter 10Algorithm chapter 10
Algorithm chapter 10
 
UNIT -IV DAA.pdf
UNIT  -IV DAA.pdfUNIT  -IV DAA.pdf
UNIT -IV DAA.pdf
 
Compositional Program Analysis using Max-SMT
Compositional Program Analysis using Max-SMTCompositional Program Analysis using Max-SMT
Compositional Program Analysis using Max-SMT
 
C&s sparse june_2010
C&s sparse june_2010C&s sparse june_2010
C&s sparse june_2010
 
Dynamic programming
Dynamic programmingDynamic programming
Dynamic programming
 
A Decomposition Technique For Solving Integer Programming Problems
A Decomposition Technique For Solving Integer Programming ProblemsA Decomposition Technique For Solving Integer Programming Problems
A Decomposition Technique For Solving Integer Programming Problems
 
A New Lagrangian Relaxation Approach To The Generalized Assignment Problem
A New Lagrangian Relaxation Approach To The Generalized Assignment ProblemA New Lagrangian Relaxation Approach To The Generalized Assignment Problem
A New Lagrangian Relaxation Approach To The Generalized Assignment Problem
 
Np
NpNp
Np
 
7f44bdd880a385b7c1338293ea4183f930ea
7f44bdd880a385b7c1338293ea4183f930ea7f44bdd880a385b7c1338293ea4183f930ea
7f44bdd880a385b7c1338293ea4183f930ea
 
Probabilistic Abductive Logic Programming using Possible Worlds
Probabilistic Abductive Logic Programming using Possible WorldsProbabilistic Abductive Logic Programming using Possible Worlds
Probabilistic Abductive Logic Programming using Possible Worlds
 
NON LINEAR PROGRAMMING
NON LINEAR PROGRAMMING NON LINEAR PROGRAMMING
NON LINEAR PROGRAMMING
 
Deep VI with_beta_likelihood
Deep VI with_beta_likelihoodDeep VI with_beta_likelihood
Deep VI with_beta_likelihood
 
Introduction to Max-SAT and Max-SAT Evaluation
Introduction to Max-SAT and Max-SAT EvaluationIntroduction to Max-SAT and Max-SAT Evaluation
Introduction to Max-SAT and Max-SAT Evaluation
 
Analysis and Design of Algorithms notes
Analysis and Design of Algorithms  notesAnalysis and Design of Algorithms  notes
Analysis and Design of Algorithms notes
 

Recently uploaded

TrustArc Webinar - 2024 Global Privacy Survey
TrustArc Webinar - 2024 Global Privacy SurveyTrustArc Webinar - 2024 Global Privacy Survey
TrustArc Webinar - 2024 Global Privacy Survey
TrustArc
 
Infrastructure Challenges in Scaling RAG with Custom AI models
Infrastructure Challenges in Scaling RAG with Custom AI modelsInfrastructure Challenges in Scaling RAG with Custom AI models
Infrastructure Challenges in Scaling RAG with Custom AI models
Zilliz
 
Let's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with Slack
Let's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with SlackLet's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with Slack
Let's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with Slack
shyamraj55
 
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAU
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAUHCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAU
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAU
panagenda
 
Serial Arm Control in Real Time Presentation
Serial Arm Control in Real Time PresentationSerial Arm Control in Real Time Presentation
Serial Arm Control in Real Time Presentation
tolgahangng
 
Removing Uninteresting Bytes in Software Fuzzing
Removing Uninteresting Bytes in Software FuzzingRemoving Uninteresting Bytes in Software Fuzzing
Removing Uninteresting Bytes in Software Fuzzing
Aftab Hussain
 
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
名前 です男
 
Communications Mining Series - Zero to Hero - Session 1
Communications Mining Series - Zero to Hero - Session 1Communications Mining Series - Zero to Hero - Session 1
Communications Mining Series - Zero to Hero - Session 1
DianaGray10
 
“I’m still / I’m still / Chaining from the Block”
“I’m still / I’m still / Chaining from the Block”“I’m still / I’m still / Chaining from the Block”
“I’m still / I’m still / Chaining from the Block”
Claudio Di Ciccio
 
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdf
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfObservability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdf
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdf
Paige Cruz
 
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?Cosa hanno in comune un mattoncino Lego e la backdoor XZ?
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?
Speck&Tech
 
Driving Business Innovation: Latest Generative AI Advancements & Success Story
Driving Business Innovation: Latest Generative AI Advancements & Success StoryDriving Business Innovation: Latest Generative AI Advancements & Success Story
Driving Business Innovation: Latest Generative AI Advancements & Success Story
Safe Software
 
Mind map of terminologies used in context of Generative AI
Mind map of terminologies used in context of Generative AIMind map of terminologies used in context of Generative AI
Mind map of terminologies used in context of Generative AI
Kumud Singh
 
UiPath Test Automation using UiPath Test Suite series, part 6
UiPath Test Automation using UiPath Test Suite series, part 6UiPath Test Automation using UiPath Test Suite series, part 6
UiPath Test Automation using UiPath Test Suite series, part 6
DianaGray10
 
Building Production Ready Search Pipelines with Spark and Milvus
Building Production Ready Search Pipelines with Spark and MilvusBuilding Production Ready Search Pipelines with Spark and Milvus
Building Production Ready Search Pipelines with Spark and Milvus
Zilliz
 
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...
Neo4j
 
How to Get CNIC Information System with Paksim Ga.pptx
How to Get CNIC Information System with Paksim Ga.pptxHow to Get CNIC Information System with Paksim Ga.pptx
How to Get CNIC Information System with Paksim Ga.pptx
danishmna97
 
Pushing the limits of ePRTC: 100ns holdover for 100 days
Pushing the limits of ePRTC: 100ns holdover for 100 daysPushing the limits of ePRTC: 100ns holdover for 100 days
Pushing the limits of ePRTC: 100ns holdover for 100 days
Adtran
 
Introduction to CHERI technology - Cybersecurity
Introduction to CHERI technology - CybersecurityIntroduction to CHERI technology - Cybersecurity
Introduction to CHERI technology - Cybersecurity
mikeeftimakis1
 
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024
GraphSummit Singapore | The Art of the  Possible with Graph - Q2 2024GraphSummit Singapore | The Art of the  Possible with Graph - Q2 2024
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024
Neo4j
 

Recently uploaded (20)

TrustArc Webinar - 2024 Global Privacy Survey
TrustArc Webinar - 2024 Global Privacy SurveyTrustArc Webinar - 2024 Global Privacy Survey
TrustArc Webinar - 2024 Global Privacy Survey
 
Infrastructure Challenges in Scaling RAG with Custom AI models
Infrastructure Challenges in Scaling RAG with Custom AI modelsInfrastructure Challenges in Scaling RAG with Custom AI models
Infrastructure Challenges in Scaling RAG with Custom AI models
 
Let's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with Slack
Let's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with SlackLet's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with Slack
Let's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with Slack
 
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAU
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAUHCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAU
HCL Notes und Domino Lizenzkostenreduzierung in der Welt von DLAU
 
Serial Arm Control in Real Time Presentation
Serial Arm Control in Real Time PresentationSerial Arm Control in Real Time Presentation
Serial Arm Control in Real Time Presentation
 
Removing Uninteresting Bytes in Software Fuzzing
Removing Uninteresting Bytes in Software FuzzingRemoving Uninteresting Bytes in Software Fuzzing
Removing Uninteresting Bytes in Software Fuzzing
 
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
みなさんこんにちはこれ何文字まで入るの?40文字以下不可とか本当に意味わからないけどこれ限界文字数書いてないからマジでやばい文字数いけるんじゃないの?えこ...
 
Communications Mining Series - Zero to Hero - Session 1
Communications Mining Series - Zero to Hero - Session 1Communications Mining Series - Zero to Hero - Session 1
Communications Mining Series - Zero to Hero - Session 1
 
“I’m still / I’m still / Chaining from the Block”
“I’m still / I’m still / Chaining from the Block”“I’m still / I’m still / Chaining from the Block”
“I’m still / I’m still / Chaining from the Block”
 
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdf
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfObservability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdf
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdf
 
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?Cosa hanno in comune un mattoncino Lego e la backdoor XZ?
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?
 
Driving Business Innovation: Latest Generative AI Advancements & Success Story
Driving Business Innovation: Latest Generative AI Advancements & Success StoryDriving Business Innovation: Latest Generative AI Advancements & Success Story
Driving Business Innovation: Latest Generative AI Advancements & Success Story
 
Mind map of terminologies used in context of Generative AI
Mind map of terminologies used in context of Generative AIMind map of terminologies used in context of Generative AI
Mind map of terminologies used in context of Generative AI
 
UiPath Test Automation using UiPath Test Suite series, part 6
UiPath Test Automation using UiPath Test Suite series, part 6UiPath Test Automation using UiPath Test Suite series, part 6
UiPath Test Automation using UiPath Test Suite series, part 6
 
Building Production Ready Search Pipelines with Spark and Milvus
Building Production Ready Search Pipelines with Spark and MilvusBuilding Production Ready Search Pipelines with Spark and Milvus
Building Production Ready Search Pipelines with Spark and Milvus
 
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...
GraphSummit Singapore | The Future of Agility: Supercharging Digital Transfor...
 
How to Get CNIC Information System with Paksim Ga.pptx
How to Get CNIC Information System with Paksim Ga.pptxHow to Get CNIC Information System with Paksim Ga.pptx
How to Get CNIC Information System with Paksim Ga.pptx
 
Pushing the limits of ePRTC: 100ns holdover for 100 days
Pushing the limits of ePRTC: 100ns holdover for 100 daysPushing the limits of ePRTC: 100ns holdover for 100 days
Pushing the limits of ePRTC: 100ns holdover for 100 days
 
Introduction to CHERI technology - Cybersecurity
Introduction to CHERI technology - CybersecurityIntroduction to CHERI technology - Cybersecurity
Introduction to CHERI technology - Cybersecurity
 
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024
GraphSummit Singapore | The Art of the  Possible with Graph - Q2 2024GraphSummit Singapore | The Art of the  Possible with Graph - Q2 2024
GraphSummit Singapore | The Art of the Possible with Graph - Q2 2024
 

Primal Dual

  • 1. Carlo Lombardi, June 2008 Theoretical Computer Science Primal-Dual Algorithms A brief survey of Primal-Dual Algorithms as an approximation technique for optimization problems Scribe: Carlo Lombardi [email_address]
  • 2.
  • 3.
  • 4. Carlo Lombardi, June 2008 Theoretical Computer Science Minimum Weighted Vertex Cover Vertex Cover Problem “ Each edge is covered by at least one node” + Weighted Verteces “ Each vertex has a weight” + Minimization of total weight “ Minimize the total weight” = Minimum Weighted Vertex Cover (WVC)
  • 5. Carlo Lombardi, June 2008 Theoretical Computer Science WVC: ILP and LP formulation We formulate the WVC as an Integer Linear Program (ILP) defining a variable x i for each vertex ( x i =1 if vertex i belongs to the cover, 0 otherwise). ILP FORMULATION LP FORMULATION by relaxing integrality constraints
  • 6. Carlo Lombardi, June 2008 Theoretical Computer Science WVC: Rounding the LP solution Primal-Dual Method We need to solve LP formulation …it can be expensive for problems having many constraints!!! Can we do something clever?
  • 7. Carlo Lombardi, June 2008 Theoretical Computer Science A different approach to LP relaxations: Primal-Dual strategy Main idea: !!! Don’t solve LP totally !!! Obtain a feasible integral solution to the LP ( Primal) from scratch using a related LP ( Dual ) to guide your decision . LP Primal LP Dual Good approximated solution “ Solve me” “ I’ll be your guide”
  • 8. Carlo Lombardi, June 2008 Theoretical Computer Science P-D strategy: Background theoretic properties (1/2) PRIMAL DUAL (Weak Duality) For any feasible Primal-Dual solution pair (x,y) : = if (x,y) is optimal (Strong Duality) If either the Primal or Dual have bounded optimal solution, the both of them do. Moreover, their objective functions values are qual. That is: (Complementary Slackness) Let (x,y) be a solutions to a primal-dual pair of LPs with bounded optima. Then x and y are both optimal iff all of the following hold
  • 9. Carlo Lombardi, June 2008 Theoretical Computer Science P-D strategy: Background theoretic properties (2/2) (Weak Duality) For any feasible Primal-Dual solution pair (x,y) : The dual solution is a lover bound for primal solution = if (x,y) is optimal (Strong Duality) If either the Primal or Dual have bounded optimal solution, the both of them do. Moreover, their objective functions values are qual. That is: At the optimum the evaluation of solutions coincides (Complementary Slackness) Let (x,y) be a solutions to a primal-dual pair of LPs with bounded optima. Then x and y are both optimal iff all of the following hold Only If a dual constraints is tight the corresponding primal variables can be greater than 0 (it can participate to the primal solution)
  • 10. Carlo Lombardi, June 2008 Theoretical Computer Science Primal-Dual strategy
  • 11.
  • 12. Carlo Lombardi, June 2008 Theoretical Computer Science Analysis of Program 2.7 (Weak Duality) Note that for every it holds: (1) The o.f. is infact From the (1) Because we are considering all vertices in V Each edge in E is taken two times
  • 13.