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New NewtonSolver._residual0 initialisation (residual) #3611

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New NewtonSolver._residual0 initialisation (residual) #3611

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b67d74e
New NewtonSolver._residual0 initialisation (residual)
SalzmanA Jan 30, 2025
4392aa8
Merge branch 'main' into newton_residual_init
jorgensd Jan 31, 2025
c83d891
Fix indentation errors
SalzmanA Feb 16, 2025
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13 changes: 6 additions & 7 deletions cpp/dolfinx/nls/NewtonSolver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -169,7 +169,10 @@ std::pair<int, bool> nls::petsc::NewtonSolver::solve(Vec x)
// Check convergence
bool newton_converged = false;
if (convergence_criterion == "residual")
{
std::tie(_residual, newton_converged) = this->_converged(*this, _b);
_residual0 = _residual;
}
else if (convergence_criterion == "incremental")
{
// We need to do at least one Newton step with the ||dx||-stopping
Expand Down Expand Up @@ -215,13 +218,6 @@ std::pair<int, bool> nls::petsc::NewtonSolver::solve(Vec x)
if (_system)
_system(x);
_fnF(x, _b);
// Initialize _residual0
if (_iteration == 1)
{
PetscReal _r = 0.0;
VecNorm(_dx, NORM_2, &_r);
_residual0 = _r;
}

// Test for convergence
if (convergence_criterion == "residual")
Expand All @@ -232,6 +228,9 @@ std::pair<int, bool> nls::petsc::NewtonSolver::solve(Vec x)
// set.
if (_iteration == 1)
{
PetscReal _r = 0.0;
VecNorm(_dx, NORM_2, &_r);
_residual0 = _r;
_residual = 1.0;
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Unrelated to the PR, but I think "residual" initialization _residual = 1.0 for the incremental criterion should happen above, outside of the loop just as it does for residual criterion. In the current code, even if the first ||dx|| < atol I would have to wait one additional iteration.

Besides the naming is not great and what we call "residual" for incremental criterion is actually increment norm...

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I think this piece of code could be completely refactored so that the convergence criterion can be switched out based on passing a different std::function?

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It can? You can do set_convergence_check?
https://github.com/search?q=repo%3AFEniCS%2Fdolfinx%20set_convergence_check&type=code
If you mean that we should have a function that includes the modification of the tolerances, I'm not sure that is worth-while.

newton_converged = false;
}
Expand Down