Ordering

The monomial ordering can be changed by calling change_ordering (Ordering.code), where code can be either lp (lexicographical ordering), dlex (degree lexicographical ordering), dp_asc (degree reverse lexicographical ordering with ascending variable ordering), block_dlex or block_dp_asc (for ordering composed out of blocks in the corresponding ordering). When using block ordering, after changing to that ordering, blocks have to be defined using the append_ring_block function.

In contrast to the lexicographical, degree lexicographical ordering, and the degree reverse lexicographical ordering in SINGULAR, our degree reverse lexicographical ordering has a reverse variable order (the first ring variable is smaller than the second, the second smaller than the third). This is a result of the fact, that efficient implementation of monomial orderings using ZDD structures is quite difficult (and the performance depends on the ordering).


Subsections

2011-02-10