From e2ad7378481c18c4ae00723d8845eac98b04858a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?B=C3=A5rd=20Skaflestad?= <Bard.Skaflestad@sintef.no>
Date: Tue, 10 Oct 2023 18:25:24 +0200
Subject: [PATCH] Make Number of Initial Global Iterations Configurable

The NLDD solver would always take one global non-linear (Newton)
iteration before starting the local non-linear iterations.  This
commit introduces a new command-line parameter,

    --nldd-num-initial-newton-iter (NlddNumInitialNewtonIter)

which allows the user to configure this value at runtime.  The
default value, 1, preserves the current behaviour.
---
 opm/simulators/flow/BlackoilModelEbos.hpp           | 12 ++++++------
 opm/simulators/flow/BlackoilModelParametersEbos.hpp | 12 ++++++++++++
 2 files changed, 18 insertions(+), 6 deletions(-)

diff --git a/opm/simulators/flow/BlackoilModelEbos.hpp b/opm/simulators/flow/BlackoilModelEbos.hpp
index de556497f..45d73d699 100644
--- a/opm/simulators/flow/BlackoilModelEbos.hpp
+++ b/opm/simulators/flow/BlackoilModelEbos.hpp
@@ -369,13 +369,13 @@ namespace Opm {
                 convergence_reports_.back().report.reserve(11);
             }
 
-            if (iteration == 0) {
-                return nonlinearIterationNewton(iteration, timer, nonlinear_solver);
+            if ((this->param_.nonlinear_solver_ != "nldd") ||
+                (iteration < this->param_.nldd_num_initial_newton_iter_))
+            {
+                return this->nonlinearIterationNewton(iteration, timer, nonlinear_solver);
             }
-            if (param_.nonlinear_solver_ == "nldd") {
-                return nlddSolver_->nonlinearIterationNldd(iteration, timer, nonlinear_solver);
-            } else {
-                return nonlinearIterationNewton(iteration, timer, nonlinear_solver);
+            else {
+                return this->nlddSolver_->nonlinearIterationNldd(iteration, timer, nonlinear_solver);
             }
         }
 
diff --git a/opm/simulators/flow/BlackoilModelParametersEbos.hpp b/opm/simulators/flow/BlackoilModelParametersEbos.hpp
index dfe740723..1cddef6a0 100644
--- a/opm/simulators/flow/BlackoilModelParametersEbos.hpp
+++ b/opm/simulators/flow/BlackoilModelParametersEbos.hpp
@@ -208,6 +208,10 @@ struct LocalToleranceScalingCnv {
     using type = UndefinedProperty;
 };
 template<class TypeTag, class MyTypeTag>
+struct NlddNumInitialNewtonIter {
+    using type = UndefinedProperty;
+};
+template<class TypeTag, class MyTypeTag>
 struct NumLocalDomains {
     using type = UndefinedProperty;
 };
@@ -407,6 +411,11 @@ struct LocalToleranceScalingCnv<TypeTag, TTag::FlowModelParameters> {
     static constexpr type value = 0.01;
 };
 template<class TypeTag>
+struct NlddNumInitialNewtonIter<TypeTag, TTag::FlowModelParameters> {
+    using type = int;
+    static constexpr auto value = type{1};
+};
+template<class TypeTag>
 struct NumLocalDomains<TypeTag, TTag::FlowModelParameters> {
     using type = int;
     static constexpr auto value = 0;
@@ -558,6 +567,7 @@ namespace Opm
         double local_tolerance_scaling_mb_;
         double local_tolerance_scaling_cnv_;
 
+        int nldd_num_initial_newton_iter_{1};
         int num_local_domains_{0};
         double local_domain_partition_imbalance_{1.03};
         std::string local_domain_partition_method_;
@@ -612,6 +622,7 @@ namespace Opm
             max_local_solve_iterations_ = EWOMS_GET_PARAM(TypeTag, int, MaxLocalSolveIterations);
             local_tolerance_scaling_mb_ = EWOMS_GET_PARAM(TypeTag, double, LocalToleranceScalingMb);
             local_tolerance_scaling_cnv_ = EWOMS_GET_PARAM(TypeTag, double, LocalToleranceScalingCnv);
+            nldd_num_initial_newton_iter_ = EWOMS_GET_PARAM(TypeTag, int, NlddNumInitialNewtonIter);
             num_local_domains_ = EWOMS_GET_PARAM(TypeTag, int, NumLocalDomains);
             local_domain_partition_imbalance_ = std::max(1.0, EWOMS_GET_PARAM(TypeTag, double, LocalDomainsPartitioningImbalance));
             local_domain_partition_method_ = EWOMS_GET_PARAM(TypeTag, std::string, LocalDomainsPartitioningMethod);
@@ -672,6 +683,7 @@ namespace Opm
             EWOMS_REGISTER_PARAM(TypeTag, int, MaxLocalSolveIterations, "Max iterations for local solves with NLDD nonlinear solver.");
             EWOMS_REGISTER_PARAM(TypeTag, Scalar, LocalToleranceScalingMb, "Set lower than 1.0 to use stricter convergence tolerance for local solves.");
             EWOMS_REGISTER_PARAM(TypeTag, Scalar, LocalToleranceScalingCnv, "Set lower than 1.0 to use stricter convergence tolerance for local solves.");
+            EWOMS_REGISTER_PARAM(TypeTag, int, NlddNumInitialNewtonIter, "Number of initial global Newton iterations when running the NLDD nonlinear solver.");
             EWOMS_REGISTER_PARAM(TypeTag, int, NumLocalDomains, "Number of local domains for NLDD nonlinear solver.");
             EWOMS_REGISTER_PARAM(TypeTag, Scalar, LocalDomainsPartitioningImbalance, "Subdomain partitioning imbalance tolerance. 1.03 is 3 percent imbalance.");
             EWOMS_REGISTER_PARAM(TypeTag, std::string, LocalDomainsPartitioningMethod, "Subdomain partitioning method. "