The Density Matrix Renormalization Group (DMRG) is a numerical method used to describe quantum many-body physics of strongly correlated electronic systems, with applicability to condensed matter theory. This method is used to calculate the dominant eigenvalues of the Hamiltonian in a Hilbert Space. It accuracy can be compared to the Exact Diagonalization (ED), but can be applied to a larger system. The DMRG method uses a relatively modest amount of computational power. Since 1992, when first proposed by S. R. White, it has been used by many scientist who proposed changes to improve it efficiency.
The DMRG++ is the implementation of the DMRG in C++ programming language. An input file with the initial data values is needed to start the code. In this file, that is written in plain text format, is difficult to address any errors. We constructed a PERL script capable of convert this plain text format of the input file to the JSON format. Using the script we converted the original data files to the JSON format. Then, we made all the necessary changes to the DMRG++ code to accept the new type of input file. It was necessary to modify many parts of the code, to make it accept the data in the new format.