ITensor / ITensor/ITensorNetworks.jl

Early stopping of square root BP

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Dominant language
Julia
Stars
128
Forks
23
Avg merge
4d 7h
Merged PRs (30d)
7

Description

"Square root BP" as defined in Eq. (25) of ^1 is introduced in #100, but without an early stopping criteria. Early stopping is a bit more subtle since in general there is an arbitrary unitary gauge degree of freedom of the "square root message tensors", which could be fixed in various ways, such as by squaring them, using a unique factorization like a positive QR or polar decomposition, using the singular values of the square root message tensors, etc. This is a reminder to implement that.

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reading Eq. (25) in the linked paper and the square root BP implementation introduced in issue #100. The issue leaves the gauge handling and stopping criterion open, so first determine an invariant criterion and its expected behavior; done would mean early stopping is implemented for square root BP and validated against the relevant behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
julia
Domain
backend
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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