Given an undirected graph
G(V,E), how fast can we detect if
G is triangle-free ? Cubic time is obvious. Let
A be the adjacency matrix of G. We can detect triangle-freeness of
G in the same complexity as multiplying two boolean matrices (
AxA) (duh !!). This simple algorithm is the
best known !! In other words, following is the open problem :
- Is testing triangle-freeness as difficult as the Boolean multiplication of two |V| x |V | matrices?
A recent paper
[1] addressess this problem partially. In a related note, the complexity of all pairs shortest paths (APSP) is still
unresolved. Is APSP (for undirected graphs) as difficult as the Boolean multiplication of two |V| x |V | matrices?
[1] N. Alon, T. Kaufman, M. Krivelevich, and D. Ron. Testing triangle-freeness in general graphs. Proceedings of the 17th Annual ACM-SIAM Symposium on Discrete Algorithms (SODA), pp. 279-288, 2006.
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