S = toricIndispensableSet A
I = toricIndispensableSet(A, R)
A binomial $x^u - x^v$ of a toric ideal $I_A$ is called indispensable if it belongs to every minimal Markov basis of A. The set of all indispensable elements is called the indispensable set, and is often denoted with $S(A)$.
This method computes the indispensable set of a matrix $A$ and returns the indispensibles as the rows of a matrix. Similarly to markovBases, if a ring $R$ is supplied, then the result is an ideal generated by the indispensable set.
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If the optional argument ReturnFiberValues is set to true, then the function instead returns the list of fibers of the indispensable binomials.
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The function computes the indispensable elements by checking the connected components of the fiber graph of $A$; see fiberGraph. A fiber gives rise to an indispensable element if and only if it has exactly two connected components and each component contains a single a single point in the fiber.
The object toricIndispensableSet is a method function with options.
The source of this document is in AllMarkovBases.m2:1024:0.