One of the ways to invert a map is to find a nonzero minor of a variant of the jacobianDualMatrix. This function controls how many minors (heuristically chosen via FastMinors
) to check before switching to another strategy (involving computing a syzygy). Setting it to zero will mean no minors are checked. If it is left as null (the default), these functions will determine a value using a heuristic that depends on the varieties involved.