ORNL / ORNL/ReSolve

Add a getter for the preconditioned initial residual from iterative solvers.

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Dominant language
C++
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Description

Summary

Add a function to get the preconditioned initial residual from the iterative solvers in ReSolve.

Rationale

When using an iterative linear solver in SUNDIALS with the IDA solver, a function that returns the initial preconditioned residual $P^{-1}(b-Ax)$ is required.

Description

A getter for the initial residual vector in either SystemSolver or the iterative linear solver classes themselves.

Alternatively, this could be calculated in SUNDIALS, but it would require a Matvec operation.

Additional information

No response

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First steps

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Research direction

Start by locating SystemSolver and the iterative solver classes mentioned in the issue, then inspect how the initial preconditioned residual is computed and stored. Determine which API should expose P^{-1}(b-Ax) to SUNDIALS without requiring an additional Matvec; done means the residual vector is accessible through a clear getter in the selected solver interface.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
hpc
Issue type
Feature
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
48/100

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