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snes solver: Consider timestep change at output #3180

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Merged
Parent: ARKODE_MRI interface
merged 1 commit into from
Oct 15, 2025
Merged

snes solver: Consider timestep change at output #3180

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93 changes: 45 additions & 48 deletions src/solver/impls/snes/snes.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -1069,70 +1069,67 @@ int SNESSolver::run() {
}
#endif // PETSC_VERSION_GE(3,20,0)

if (looping) {

if (pid_controller) {
// Changing the timestep.
// Note: The preconditioner depends on the timestep,
// so we recalculate the jacobian and the preconditioner
// every time the timestep changes

timestep = pid(timestep, nl_its);

// NOTE(malamast): Do we really need this?
// Recompute Jacobian (for now)
if (saved_jacobian_lag == 0) {
SNESGetLagJacobian(snes, &saved_jacobian_lag);
SNESSetLagJacobian(snes, 1);
}
if (pid_controller) {
// Changing the timestep.
// Note: The preconditioner depends on the timestep,
// so we recalculate the jacobian and the preconditioner
// every time the timestep changes

} else {
timestep = pid(timestep, nl_its);

// Consider changing the timestep.
// Note: The preconditioner depends on the timestep,
// so if it is not recalculated the it will be less
// effective.
if ((nl_its <= lower_its) && (timestep < max_timestep)
&& (steps_since_snes_failure > 2)) {
// Increase timestep slightly
timestep *= timestep_factor_on_lower_its;

timestep = std::min(timestep, max_timestep);

// Note: Setting the SNESJacobianFn to NULL retains
// previously set evaluation function.
//
// The SNES Jacobian is a combination of the RHS Jacobian
// and a factor involving the timestep.
// Depends on equation_form
// -> Probably call SNESSetJacobian(snes, Jfd, Jfd, NULL, fdcoloring);

if (static_cast<BoutReal>(lin_its) / nl_its > 4) {
// Recompute Jacobian (for now)
if (saved_jacobian_lag == 0) {
SNESGetLagJacobian(snes, &saved_jacobian_lag);
SNESSetLagJacobian(snes, 1);
}
}
// NOTE(malamast): Do we really need this?
// Recompute Jacobian (for now)
if (saved_jacobian_lag == 0) {
SNESGetLagJacobian(snes, &saved_jacobian_lag);
SNESSetLagJacobian(snes, 1);
}

} else if (nl_its >= upper_its) {
// Reduce timestep slightly
timestep *= timestep_factor_on_upper_its;
} else {

// Recompute Jacobian
// Consider changing the timestep.
// Note: The preconditioner depends on the timestep,
// so if it is not recalculated the it will be less
// effective.
if ((nl_its <= lower_its) && (timestep < max_timestep)
&& (steps_since_snes_failure > 2)) {
// Increase timestep slightly
timestep *= timestep_factor_on_lower_its;

timestep = std::min(timestep, max_timestep);

// Note: Setting the SNESJacobianFn to NULL retains
// previously set evaluation function.
//
// The SNES Jacobian is a combination of the RHS Jacobian
// and a factor involving the timestep.
// Depends on equation_form
// -> Probably call SNESSetJacobian(snes, Jfd, Jfd, NULL, fdcoloring);

if (static_cast<BoutReal>(lin_its) / nl_its > 4) {
// Recompute Jacobian (for now)
if (saved_jacobian_lag == 0) {
SNESGetLagJacobian(snes, &saved_jacobian_lag);
SNESSetLagJacobian(snes, 1);
}
}

} else if (nl_its >= upper_its) {
// Reduce timestep slightly
timestep *= timestep_factor_on_upper_its;

// Recompute Jacobian
if (saved_jacobian_lag == 0) {
SNESGetLagJacobian(snes, &saved_jacobian_lag);
SNESSetLagJacobian(snes, 1);
}
}
}
snes_failures = 0;
} while (looping);

if (!matrix_free) {
ASSERT2(simtime >= target);
ASSERT2(simtime - dt < target);
ASSERT2(simtime - dt <= target);
// Stepped over output timestep => Interpolate
// snes_x is the solution at t = simtime
// x0 is the solution at t = simtime - dt
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