The computational time ratio to the total time cost for the most time-consuming parts. Applying the Hamiltonian to the wavefunction (|ϕ〉 = H|ψ〉, denoted by ×) is the core operation for diagonalizing the Hamiltonian. The truncation procedure (°) contains diagonalizing the reduced density matrix (▽) and projecting the operator on the new basis (Δ). The former can be considered as the singular value decomposition (SVD) of the superblock wavefunction.