Questions tagged [hard-instances]

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5
votes
0answers
85 views

Computational depth and p-time hard instances

After reading the nice results of the paper: "Worst-Case Running Times for Average-Case Algorithms" by Antunes and Fortnow, I was wondering about the existence of further results linking basic ...
12
votes
3answers
331 views

Does there exist a hardest DCFL?

Greibach famously defined a language $H$, the so-called nondeterministic version of $D_2$, such that any CFL is an inverse morphic image of $H$. Does there exist a similar statement with DCFL, ...
3
votes
1answer
546 views

Easier and Harder instances of NP-complete problems?

Following previous questions here and here around $NP$-complete problems (and P vs NP). Are there "easier" or "harder" (sets of) instances of an $NP$-complete problem? If yes (which i assume), how a ...
11
votes
2answers
695 views

What's the correlation between treewidth and instance hardness for random 3-SAT?

This recent paper from FOCS2013, Strong Backdoors to Bounded Treewidth SAT by Gaspers and Szeider talks about the link between the treewidth of the SAT clause graph and instance hardness. For ...
10
votes
1answer
387 views

Examples of hard instances for Goemans and Williamson algorithm

I'm interested in the explicit examples of graphs for which application of Goemans and Williamson algorithm for approximating maximum cuts results in 0.878…-approximation factor. The algorithm to ...
10
votes
3answers
499 views

Is embedding a solution feasible for SAT?

I am interested in "hard" individual instances of NP-complete problems. Ryan Williams discussed the SAT0 problem at Richard Lipton's blog. SAT0 asks whether a SAT instance has the specific solution ...