big o - Example of an impractical algorithm known to be in P? -

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it's accepted problems can solved in polynomial time "tractable" while algorithms requiring more time intractable. of course, being solvable in polynomial time says nothing of absolute efficiency; example, runs in time n1000 impractical in practice.

although i've seen fair number of polynomial-time algorithms, i've never seen 1 practical problem ran in more o(n4), original version of edmonds' matching algorithm.

my question is: is there well-known problem best polynomial-time algorithm impractical real inputs? can construct simple contrived problems utterly useless, i'm curious if there's famous problem best known solution both polynomial-time , entirely infeasible.

edit: clarify, should i'm looking algorithm enormous exponent on problem size, rather hard-to-implement algorithm or 1 huge constant factor. moron pointed out, there many famous impractical algorithms great asymptotic behavior.

primes in p: aks primality test, complexity o(n6), n = log n number of bits used encode prime candidate.

while beautiful theoretical result, testing primality performed miller-rabin test, or other randomized algorithms alike.


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