Once the molecular formula satisfies the graph existence criteria, the hydrogen distribution is performed to build a list of degrees. MAYGEN then starts the actual construction of candidate structures for each degree. The structures are built in a block-wise manner. The algorithm is based on the node degrees that correspond to the atom valences. The initial partition of the atoms, based on their element symbols, defines the blocks of the matrix (Figure ). Here, the matrix is split into parts based on the initial node partition with t entries. Image adapted from . λ