  ${\mathcal H}\Phi$ [$aitch$-$phi$] is a program package based on the
Lanczos-type eigenvalue solution applicable to a broad range of quantum lattice
models, i.e., arbitrary quantum lattice models with two-body interactions,
including the Heisenberg model, the Kitaev model, the Hubbard model and the
Kondo-lattice model. While it works well on PCs and PC-clusters, ${\mathcal
H}\Phi$ also runs efficiently on massively parallel computers, which
considerably extends the tractable range of the system size. In addition,
unlike most existing packages, ${\mathcal H}\Phi$ supports finite-temperature
calculations through the method of thermal pure quantum (TPQ) states. In this
paper, we explain theoretical background and user-interface of ${\mathcal
H}\Phi$. We also show the benchmark results of ${\mathcal H}\Phi$ on
supercomputers such as the K computer at RIKEN Advanced Institute for
Computational Science (AICS) and SGI ICE XA (Sekirei) at the Institute for the
Solid State Physics (ISSP).
