Internet Engineering Czesław Smutnicki Discrete Mathematics – Computational Complexity.

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Presentation transcript:

Internet Engineering Czesław Smutnicki Discrete Mathematics – Computational Complexity

CONTENT S Asymptotic notation Decision/optimization problems Calculation models Turing machines Problem, instances, data coding Complexity classes Polynomial-time algorithms Theory of NP-completness Approximate methods Quality measures of approximation Analysis of quality measures Calculation cost Competitive analysis (on-line algorithms) Inapproximality theory

ASYMPTOTIC NOTATION – symbol O(n) Definition Examples

ASYMPTOTIC NOTATION – symbol  (n) Definition Examples

ASYMPTOTIC NOTATION – symbol  (n) Definition Examples

ASYMPTOTIC NOTATION - symbol o(n) Definition Examples

ASYMPTOTIC NOTATION - symbol  (n) Definition Examples

DECISION/OPTIMIZATION PROBLEMS decision problem: answer yes-no 2-partition problem: given numbers. Does a set exist such that optimization problem: find min or max of the goal function value knapsack problem: given numbers, and. Find the set s uch that, any optimization problem can be transformed into decision problem knapsack problem: given numbers,, and. Does a set exist s uch that,

CALCULATION MODELS Simple machine Finite-state machine Automata: Mealy Moore Deterministic/non-deterministic finite automata S o i io

DETERMINISTIC TURING MACHINE s …

NON-DETERMINISTIC TURING MACHINE s …

CODING Instance I/ Problem P Decimal coding of I Binary coding of I Unary coding of I Data string x(I) Size N(I) of the instance I Coding of numbers and structural elements

COMPUTATIONAL COMPLEXITY FUNCTION DEPENDS ON: Coding rule Model of calculations (DTM)

FUNDAMENTAL COMPLEXITY CLASSES Polynomial time algorithm O(p(n)), p – polynom ial, solvable by DTM, P class Exponential time algorithm NP class, solvable in O(p(n)) on NDTM = solvable in O(2 p(n) ) on DTM 1060 n10 -5 s6·10 -5 s n3n s2·10 -1 s n5n s13 m 2n2n s3366 y

NP COMPLETE PROBLEMS POLYNOMIAL TIME TRANSFORMATION PROBLEM P1 IS NP-COMPLETE IF P1 BELONGS TO NP CLASS AND FOR ANY P2 FROM NP CLASS, P2 IS POLYNOMIALLY TRANSFORMABLE TO P1 PROBLEM IS PSEUDO-POLYNOMIAL (NPI CLASS) IF ITS COMPUTATIONAL COMPLEXITY FUNCTION IS A POLYNOMIAL OF N(I) AND MAX(I)

COMPLEXITY CLASSES NP CLASS P CLASS NPI CLASS NP COMPLETE CLASS STRONGLY NP COMPLETE CLASS

Thank you for your attention DISCRETE MATHEMATICS Czesław Smutnicki