lanczos_arpack

• full name: tenpy.linalg.krylov_based.lanczos_arpack

• parent module: tenpy.linalg.krylov_based

• type: function

tenpy.linalg.krylov_based.lanczos_arpack(H, psi, options={})

Use scipy.sparse.linalg.eigsh() to find the ground state of H.

This function has the same call/return structure as lanczos(), but uses the ARPACK package through the functions speigsh() instead of the custom lanczos implementation in LanczosGroundState. This function is mostly intended for debugging, since it requires to convert the vector from np_conserved Array into a flat numpy array and back during each matvec-operation!

Parameters:

• H – See LanczosGroundState. H and psi should have/use labels.

• psi – See LanczosGroundState. H and psi should have/use labels.

• options – See LanczosGroundState. H and psi should have/use labels.

Returns:

• E0 (float) – Ground state energy.

• psi0 (Array) – Ground state vector.