 Hermite normal form

The Hermite normal form is a canonical triangular form for an integer matrix under integer elementary row operations or, in the column convention, column operations. In the row convention for a nonsingular rank-two matrix, positive diagonal entries and reduction of the upper-right entry modulo the lower diagonal entry give the row Hermite normal form in rank two.

Hermite Normal Form (HNF) is a special form of a matrix used in linear algebra, particularly in the context of integer linear algebra. A matrix is in Hermite Normal Form if it satisfies the following conditions: 1. It is an upper triangular matrix: All entries below the main diagonal are zero. 2. The diagonal entries are strictly positive: Each diagonal entry is a positive integer.