void
NonlinearSolver<PhysicalModel>::detectOscillations(const std::vector<std::vector<double>>& residual_history,
const int it,
bool& oscillate, bool& stagnate) const
{
// The detection of oscillation in two primary variable results in the report of the detection
// of oscillation for the solver.
// Only the saturations are used for oscillation detection for the black oil model.
// Stagnate is not used for any treatment here.
if ( it < 2 ) {
oscillate = false;
stagnate = false;
return;
}
stagnate = true;
int oscillatePhase = 0;
const std::vector<double>& F0 = residual_history[it];
const std::vector<double>& F1 = residual_history[it - 1];
const std::vector<double>& F2 = residual_history[it - 2];
for (int p= 0; p < model_->numPhases(); ++p){
const double d1 = std::abs((F0[p] - F2[p]) / F0[p]);
const double d2 = std::abs((F0[p] - F1[p]) / F0[p]);
oscillatePhase += (d1 < relaxRelTol()) && (relaxRelTol() < d2);
// Process is 'stagnate' unless at least one phase
// exhibits significant residual change.
stagnate = (stagnate && !(std::abs((F1[p] - F2[p]) / F2[p]) > 1.0e-3));
}
oscillate = (oscillatePhase > 1);
}
int
NewtonSolver<PhysicalModel>::
step(const double dt,
ReservoirState& reservoir_state,
WellState& well_state)
{
// Do model-specific once-per-step calculations.
model_->prepareStep(dt, reservoir_state, well_state);
// For each iteration we store in a vector the norms of the residual of
// the mass balance for each active phase, the well flux and the well equations.
std::vector<std::vector<double>> residual_norms_history;
// Assemble residual and Jacobian, store residual norms.
model_->assemble(reservoir_state, well_state, true);
residual_norms_history.push_back(model_->computeResidualNorms());
// Set up for main Newton loop.
double omega = 1.0;
int iteration = 0;
bool converged = model_->getConvergence(dt, iteration);
const int sizeNonLinear = model_->sizeNonLinear();
V dxOld = V::Zero(sizeNonLinear);
bool isOscillate = false;
bool isStagnate = false;
const enum RelaxType relaxtype = relaxType();
int linearIterations = 0;
// ---------- Main Newton loop ----------
while ( (!converged && (iteration < maxIter())) || (minIter() > iteration)) {
// Compute the Newton update to the primary variables.
V dx = model_->solveJacobianSystem();
// Store number of linear iterations used.
linearIterations += model_->linearIterationsLastSolve();
// Stabilize the Newton update.
detectNewtonOscillations(residual_norms_history, iteration, relaxRelTol(), isOscillate, isStagnate);
if (isOscillate) {
omega -= relaxIncrement();
omega = std::max(omega, relaxMax());
if (model_->terminalOutputEnabled()) {
std::cout << " Oscillating behavior detected: Relaxation set to " << omega << std::endl;
}
}
stabilizeNewton(dx, dxOld, omega, relaxtype);
// Apply the update, the model may apply model-dependent
// limitations and chopping of the update.
model_->updateState(dx, reservoir_state, well_state);
// Assemble residual and Jacobian, store residual norms.
model_->assemble(reservoir_state, well_state, false);
residual_norms_history.push_back(model_->computeResidualNorms());
// increase iteration counter
++iteration;
converged = model_->getConvergence(dt, iteration);
}
if (!converged) {
if (model_->terminalOutputEnabled()) {
std::cerr << "WARNING: Failed to compute converged solution in " << iteration << " iterations." << std::endl;
}
return -1; // -1 indicates that the solver has to be restarted
}
linearIterations_ += linearIterations;
newtonIterations_ += iteration;
linearIterationsLast_ = linearIterations;
newtonIterationsLast_ = iteration;
// Do model-specific post-step actions.
model_->afterStep(dt, reservoir_state, well_state);
return linearIterations;
}