Correction vector

[adeorlandini]

Hi, I was doing dynamics calculations using the time evolution of the ground state. However I wonder if there is an implementation of itensor for correction vector? if it wasn’t the case, could it be implemented in a “simple” way with the current MPS paradigm using by itensor?

Cheers

[miles]

Thanks for the question, but no we don’t have an implementation of correction vector in ITensor and I don’t know of one. The basic pattern is that it uses the DMRG algorithm with the main change that instead of solving an eigenvalue problem A x = \lambda x for x it solves an Ax = b problem.

So in principle you could take our dmrg function here: https://github.com/ITensor/ITensors.jl/blob/40fc8deaf94a75e8ae6c00e97d6cf234fdf14a57/src/mps/dmrg.jl#L116
and change the part that calls the eigsolve function
https://github.com/ITensor/ITensors.jl/blob/40fc8deaf94a75e8ae6c00e97d6cf234fdf14a57/src/mps/dmrg.jl#L221
which is a function defined by the library
KrylovKit.jl, and modify the code to instead call the linsolve function which is documented here.

We are also currently working on a new implementation of our DMRG code that will make it easier to switch out the solver and define custom solvers. I expect that will happen in a few months.

Hope that helps for now –