26 Apr 2000 02:36:07 -0400

Related articles |
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On CFL equivalence and graph isomorphism johnston.p@worldnet.att.net (Paul Johnston) (2000-04-20) |

Re: On CFL equivalence and graph isomorphism lex@cc.gatech.edu (2000-04-25) |

Re: On CFL equivalence and graph isomorphism colohan+@cs.cmu.edu (Christopher Brian Colohan) (2000-04-25) |

Re: On CFL equivalence and graph isomorphism pmoisset@altavista.net (Pablo) (2000-04-25) |

Re: On CFL equivalence and graph isomorphism ger@informatik.uni-bremen.de (George Russell) (2000-04-26) |

Re: On CFL equivalence and graph isomorphism bdm@cs.anu.edu.au (2000-04-26) |

Re: On CFL equivalence and graph isomorphism dmolnar@fas.harvard.edu (David A Molnar) (2000-04-27) |

Re: On CFL equivalence and graph isomorphism miyazaki@symbolix.cs.uoregon.edu (2000-04-27) |

From: | bdm@cs.anu.edu.au (Brendan McKay) |

Newsgroups: | comp.theory,comp.compilers |

Date: | 26 Apr 2000 02:36:07 -0400 |

Organization: | Australian National University |

Distribution: | inet |

References: | 00-04-140 00-04-167 |

Keywords: | theory |

"Paul Johnston" <johnston.p@worldnet.att.net> writes:

*> > Furthermore, what is the state of solving the Graph Isomorhism*

*> > problem? Is there no hope?*

Christopher Brian Colohan <colohan+@cs.cmu.edu> wrote:

*> I believe it has been proven to be NP-complete (I need to check in my*

*> Gary&Johnson to be sure, and I am out of town...).*

Graph isomorphism is not known to be NP-complete, nor to be in P. It

might turn out to be neither.

The practical state of the art is that only the hardest problems

cannot be solved for up to a few tens of thousands of vertices. See

http://cs.anu.edu.au/~bdm/nauty.

*> So it is possible to solve, just not in reasonable time given today's*

*> known algorithms. If anyone finds a way of efficiently solving*

*> NP-complete problems, then we will have a great deal to celebrate.*

That might not be a correct statement even if the problem is

NP-complete. It is a very common myth, though. The truth is that

people solve real-life instances of NP-complete problems every day.

Brendan.

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