NonlinearSolverEbos: put stabilizeNonlinearUpdate in compile unit

opm/simulators/flow/NonlinearSolverEbos.cpp

@@ -20,7 +20,13 @@
 #include <config.h>
 #include <opm/simulators/flow/NonlinearSolverEbos.hpp>
 
+#include <dune/common/fvector.hh>
+#include <dune/istl/bvector.hh>
+
+#include <opm/common/ErrorMacros.hpp>
+
 #include <cmath>
+#include <stdexcept>
 
 namespace Opm {
 namespace detail {
@@ -59,5 +65,56 @@ void detectOscillations(const std::vector<std::vector<double>>& residualHistory,
     oscillate = (oscillatePhase > 1);
 }
 
+template <class BVector>
+void stabilizeNonlinearUpdate(BVector& dx, BVector& dxOld,
+                              const double omega,
+                              NonlinearRelaxType relaxType)
+{
+    // The dxOld is updated with dx.
+    // If omega is equal to 1., no relaxtion will be appiled.
+
+    BVector tempDxOld = dxOld;
+    dxOld = dx;
+
+    switch (relaxType) {
+    case NonlinearRelaxType::Dampen: {
+        if (omega == 1.) {
+            return;
+        }
+        for (auto& d : dx) {
+            d *= omega;
+        }
+        return;
+    }
+    case NonlinearRelaxType::SOR: {
+        if (omega == 1.) {
+            return;
+        }
+        auto i = dx.size();
+        for (i = 0; i < dx.size(); ++i) {
+            dx[i] *= omega;
+            tempDxOld[i] *= (1.-omega);
+            dx[i] += tempDxOld[i];
+        }
+        return;
+    }
+    default:
+        OPM_THROW(std::runtime_error, "Can only handle Dampen and SOR relaxation type.");
+    }
+
+    return;
+}
+
+template<int Size> using BV = Dune::BlockVector<Dune::FieldVector<double,Size>>;
+#define INSTANCE(Size) \
+    template void stabilizeNonlinearUpdate<BV<Size>>(BV<Size>&, BV<Size>&, \
+                                                  const double, NonlinearRelaxType);
+INSTANCE(1)
+INSTANCE(2)
+INSTANCE(3)
+INSTANCE(4)
+INSTANCE(5)
+INSTANCE(6)
+
 } // namespace detail
 } // namespace Opm