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Dear Miles and Matthew,

I have noticed the Real-space parallel density matrix renormalization group (DMRG) based on ITensor2 (https://github.com/emstoudenmire/parallelDMRG). I want to use it in version 3. Can you provide this or provide some suggestions? We are dealing with long-range system and need the energy and ground state of large system size.

Thanks in advance!

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Hi, glad you are interested in ITensor and the parallel DMRG code.

Unfortunately, due to other pressing priorities, we will not have time ourselves to upgrade and test that code soon. For one thing, we are hard at work finalizing a new version of the core ITensor library in the Julia language.

So until we do get around to updating that code, there are a couple paths you could consider:

  1. are you sure you need to use parallel DMRG? How large is the system size that's necessary for your study? Are there Hamiltonian parameters you can parallelize over instead, in the sense of doing separate DMRG runs with different Hamiltonians?

  2. it would be great if you would be willing to upgrade the parallel DMRG code for us, and make the new version public. We'd be happy to credit you on the website. There is a version 2 to version 3 upgrade guide which covers the major changes in the library between those versions: http://itensor.org/docs.cgi?vers=cppv3&page=upgrade2to3
    and we could answer questions you may have about the upgrade process.

Best regards,

commented by (230 points)
Thanks a lot.
1. We have used version3.1 (ITensor speeds up calculations involving block sparse). Now the system size of long-range system is about one-hundred sites. What we need size is at least two-hundred sites.  Hamiltonian parameters is difficult to parallelize, since we do DMRG in momentum space.
2. It is great to guide. I would like to have a try of upgrade.

Best regards,
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