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Visualising the Tutte Polynomial Computation
Bennett Thompson, David J. Pearce
Victoria University of Wellington,New Zealand
Gary HaggardBucknell, USA
COMP205 Software Design and Engineering
The Tutte Polynomial
• Delete/Contract Operations:
• Tutte Definition:
T(G) = 1, if G = T(G) = xT(G/e), if e is a bridgeT(G) = yT(G-e), if e is a loopT(G) = T(G-e) + T(G/e), otherwise
G = G–e = G/e =
COMP205 Software Design and Engineering
Tutte Computation Tree
COMP205 Software Design and Engineering
Great, but why do we care?
• Many applications of Tutte polynomial– Physics, Biology and probably lots more …
• Knots– Tangled cords which can’t be unravelled
– Problem: how do we know when two knots are same?
– Tutte polynomial can be used to answer this
COMP205 Software Design and Engineering
GREAT, but why do we care?
• Many applications of Tutte polynomial– Physics, Biology and probably lots more …
• For example– Tangled cords which can’t be unravelled– Double Helix of DNA actually forms a Knot
-- N.R. Cozzarelli and A. Stasiak
COMP205 Software Design and Engineering
Optimising the Computation
• Caching previously seen graphs:
COMP205 Software Design and Engineering
Performance Data
COMP205 Software Design and Engineering
Optimising the Computation
• Degrees of Freedom– Can apply Tutte rules in any order
– Can choose any edge to delete/contract
– Our choices affect size of computation tree
• Edge Selection Heuristics– Developed heuristics: Minsdeg, Vorder
– But, why are they any good?
COMP205 Software Design and Engineering
Visualising the Computation Tree
• Tree may have > 100K nodes– How can we visualise it?
Minsdeg
Vorder
Minsdeg
Vorder
COMP205 Software Design and Engineering
To be continued …
• Edge Selection Heuristics …
– Q) How do we know why they work?– A) Visualise them!
– Q) So, does it really help?– A) Er …, I’ll tell you later !
COMP205 Software Design and Engineering
Graph Layout Algorithms?
• Simple layout algorithm used– Better ones exist that minimise crossings– But, simple approach has some
advantages…
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