Approximating P-Complete Problems (2024)

Limits to Parallel Computation: P-Completeness Theory

Raymond Greenlaw et al.

Published:

1995

Online ISBN:

9780197560518

Print ISBN:

9780195085914

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Limits to Parallel Computation: P-Completeness Theory

Raymond Greenlaw et al.

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Raymond Greenlaw,

Raymond Greenlaw

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H James Hoover,

H James Hoover

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Walter L Ruzzo

Walter L Ruzzo

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Pages

108–113

  • Published:

    June 1995

Cite

Greenlaw, Raymond, H James Hoover, and Walter L Ruzzo, 'Approximating P-Complete Problems', Limits to Parallel Computation: P-Completeness Theory (New York, 1995; online edn, Oxford Academic, 12 Nov. 2020), https://doi.org/10.1093/oso/9780195085914.003.0014, accessed 2 June 2024.

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Abstract

Suppose that finding the solution to a problem is P-complete. It is natural to ask if it is any easier to obtain an approximate solution. For decision problems this might mean considering the corresponding combinatorial optimization problem. That is, a problem in which we try to minimize or maximize a given quantity. As one might expect from the theory of NP-completeness, the answer is both yes (for example in the case of Bin Packing, Problem A.4.7) and no (for example in the case of the Lexicographically First Maximal Independent Set Size Problem, see Lemma 10.2.2.). There are several motivations for developing good NC approximation algorithms. First, in all likelihood P-complete problems cannot be solved fast in parallel. Therefore, it may be useful to approximate them quickly in parallel. Second, problems that are P- complete but that can be approximated well seem to be special boundary cases. Perhaps by examining these types of problems more closely we can improve our understanding of parallelism. Third, it is important to build a theoretical foundation for studying and classifying additional approximation problems. Finally, it may be possible to speed up sequential approximation algorithms, of NP-complete problems, using fast parallel approximations. Our goal in this section is to develop the basic theory of parallel approximation algorithms. We begin by showing that certain P-complete problems are not amenable to NC approximation algorithms. Later we present examples of P-complete problems that can be approximated well in parallel. We start by considering the Lexicographically First Maximal Independent Set Problem, introduced in Definition 7.1.1, and proven P-complete in Problem A.2.1. As defined, LFMIS it is not directly amenable to approximation. We can phrase the problem in terms of computing the size of the independent set. Definition 10.2.1 Lexicographically First Maximal Independent Set Size (LFMISsize) Given: An undirected graph G = (V, E) with an ordering on the vertices and an integer k. Problem: Is the size of the lexicographically first maximal independent set of G less than or equal to k ? The following lemma shows that computing just the size of the lexicographically first maximal independent set is P-complete.

Subject

Mathematical Theory of Computation

Collection: Oxford Scholarship Online

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FAQs

Is it possible to solve NP-complete problems? ›

(i) All NP-complete problems are solvable in polynomial time: Yes. Every problem in NP is polynomially reducible to SAT, and SAT is reducible to every NP-hard problem. Therefore, a polynomial time solution to any NP-hard problem (such as 3Col) implies that every problem in NP can be solved in polynomial time.

Why is p vs np so hard? ›

The answer is complexity. It's much more difficult to quickly find a solution to an NP problem than a P problem. Computers can easily check solutions to NP problems, but devising an algorithm that can propose solutions to NP problems in a reasonable time is much more difficult.

Is NP-hard harder than NP-complete? ›

A problem is said to be NP-hard if everything in NP can be transformed in polynomial time into it even though it may not be in NP. A problem is NP-complete if it is both in NP and NP-hard. The NP-complete problems represent the hardest problems in NP.

Is P NP justify your answer? ›

Hence, P equals NP would mean that proving mathematical theorems can be done by a simple computer program. “P equals NP would transform mathematics by allowing a computer to find a formal proof of any theorem which has a proof of a reasonable length, since formal proofs can easily be recognized in polynomial time.”

Are NP-hard problems unsolvable? ›

Some are, some are not. Boolean Satisfiability (SAT) is solvable and NP-hard (in fact, NP-complete). The Halting Problem is NP-hard and not solvable. NP hardnes and solvability is two distinct categories defined on different types of criteria.

Can humans solve NP-hard problems? ›

NP-hard problems commonly come up as human-solvable puzzles. Like Sudoku... or perhaps a more applicable problem... layout and routing of electronic components on a PCB and/or chip. Or even assembly-language register allocation (coloring and packing problem).

Has anyone solved P vs NP? ›

While the P versus NP problem is generally considered unsolved, many amateur and some professional researchers have claimed solutions.

Can AI solve P vs NP? ›

AI, with its advanced pattern recognition and data processing capabilities, is ideally positioned to tackle the P vs NP problem. Machine learning algorithms can process and analyze vast datasets much faster than humans, identifying patterns that could lead to a solution.

Is chess NP-hard? ›

Is Chess NP complete or NP hard? “Real” chess is in P because it's of finite size so all positions can be (in a theoretical, computational-complexity sense) looked up in a table. “Generalized” chess is harder than NP, but you have to define how you generalize it to larger boards.

What is the easiest NP to get? ›

What Are The Easiest Nurse Practitioner Programs to Get Into?
  • Psychiatric Mental Health Nurse Practitioner (PMHNP) Programs. ...
  • Emergency Room Nurse Practitioner Programs. ...
  • Adult-Gerontology Nurse Practitioner (AGNP) Programs. ...
  • Neonatal Nurse Practitioner (NNP) Programs. ...
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Why NP-hard problems are hardest to solve? ›

A “P problem” takes a computer “polynomial time” to complete, while an “NP-Hard problem” takes exponential time to solve because there is no known algorithm that can solve it in polynomial time.

Is traveling salesman NP-hard? ›

It is an NP-hard problem in combinatorial optimization, important in theoretical computer science and operations research.

Is P-NP a millennium problem? ›

The Clay Mathematics Institute officially designated the title Millennium Problem for the seven unsolved mathematical problems, the Birch and Swinnerton-Dyer conjecture, Hodge conjecture, Navier–Stokes existence and smoothness, P versus NP problem, Riemann hypothesis, Yang–Mills existence and mass gap, and the Poincaré ...

What is P vs NP in layman's terms? ›

'P' stands for 'Polynomial Time', problems that can be solved relatively quickly by a computer. 'NP' stands for 'Nondeterministic Polynomial Time', problems for which a solution can be checked quickly. The question (P vs NP) is whether every problem whose solution can be checked quickly can also be solved quickly.

What is P vs NP for dummies? ›

Thus, P problems are said to be easy, or tractable. A problem is called NP if its solution can be guessed and verified in polynomial time, and nondeterministic means that no particular rule is followed to make the guess.

Can NP-complete problems be solved in linear time? ›

So far we've seen a lot of good news: such-and-such a problem can be solved quickly (in close to linear time, or at least a time that is some small polynomial function of the input size).

Can all NP-complete problems be solved in polynomial time? ›

It was recently proved mathematically that memcomputing machines have the same computational power of non-deterministic Turing machines. Therefore, they can solve NP-complete problems in polynomial time and, using the appropriate architecture, with resources that only grow polynomially with the input size.

Can we solve an NP-hard problem? ›

Importantly, these problems don't have an algorithm that can solve them in polynomial time. They are called NP-hard because they are at least as hard as the hardest problems in NP class. Can np hard problems be solved? Yes, NP-hard problems can be solved, but there's a catch.

Can NP-complete problems be solved in exactly exponential time? ›

It is widely suspected that NP complete problems require exponential time. However, this has not been proved and it's still possible that there is some clever way to solve them in polynomial time.

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