MADAM defactoring

A failed defactoring technique which was experimented with during the development of column Hermite defactoring took advantage of the fact that the list of minor determinants (or simply "minors") of a mapping is guaranteed to include any common factor as its entries' GCD. So, if one simply converted a mapping to its list of minors, removed the GCD (at which point you would have what in RTT is called a canonical multimap, or wedgie), and then performed an "anti-minors" operation to get back to a mapping form, any common factors should be removed.

Inspired by Gene Ward Smith's method for computing anti-minors as described here and here, an anti-minors method was implemented in Wolfram Language. It was found that a defactoring algorithm based on Minors And Divide-out-GCG, Anti-Minors, or MADAM defactoring, does indeed work. However, it runs 10 to 20 times slower than Smith defactoring and column Hermite defactoring, and it is not compellingly easier to understand than either of them, so it is not considered to be of significant interest.

Dave Keenan and Douglas Blumeyer record a summary of their work here in case it may be helpful to anyone else who might want to iterate on this later. The other major failed experimental defactoring technique was SAD defactoring.