Add Multilevel additive schwarz (MAS) solver

[iiiian]

Changes

• Implement MAS solver
• Fix cuda setup
  • Fix cuda cmake
  • Fix AMGCL diagnostic flag pollution
  • Fix cuSolver namespace

Compile

To enable cuda, use -DPOLYSOLVE_WITH_CUDA=ON. Only cuda 13+ is supported.

Example config

Minimal

{
    "solver": "MAS",
    "MAS": {
        "absolute_tolerance": 1e-8,
        "relative_tolerance": 1e-5,
        "block_dim": 1 // 1 for scalar problem, 2 for 3D, 3 for 3D.
    }
}

Full

{
    "solver": "MAS",
    "MAS": {
        "absolute_tolerance": 1e-8,
        "relative_tolerance": 1e-5,
        "block_dim": 1, // 1 for scalar problem, 2 for 3D, 3 for 3D.
        "lazy_partitioning": true, // reuse graph partition across newton steps
        "max_iter": 5000,
        "use_preconditioned_residual_norm": false // use preconditioned norm in convergence check.
    }
}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.53%. Comparing base (96a6bd2) to head (4864eca).

Additional details and impacted files

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##             main     #102   +/-   ##
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  Coverage   80.53%   80.53%           
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  Files          49       49           
  Lines        2106     2106           
  Branches      281      280    -1     
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  Hits         1696     1696           
  Misses        410      410           

Flag	Coverage Δ
polysolve	80.53% <ø> (ø)

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