From 3b9f641f4202a7903b453385700ff7268ef7f0c9 Mon Sep 17 00:00:00 2001
From: Pratik Nayak <pratik.nayak4@gmail.com>
Date: Tue, 5 Feb 2019 14:20:12 +0100
Subject: [PATCH] Add preconditioner support.

---
 include/deal.II/lac/ginkgo_solver.h | 13 +++++++++++++
 source/lac/ginkgo_solver.cc         | 13 +++++++++++++
 tests/ginkgo/solver.cc              |  7 +++++++
 tests/ginkgo/solver.output          |  1 +
 4 files changed, 34 insertions(+)

diff --git a/include/deal.II/lac/ginkgo_solver.h b/include/deal.II/lac/ginkgo_solver.h
index 3ac50c9128..3b327511ed 100644
--- a/include/deal.II/lac/ginkgo_solver.h
+++ b/include/deal.II/lac/ginkgo_solver.h
@@ -225,6 +225,19 @@ namespace GinkgoWrappers
              std::shared_ptr<gko::Executor> executor,
              const AdditionalData &         data = AdditionalData());
 
+  /**
+   * Constructor.
+   *
+   * @p solver_control The solver control object is then used to set the
+   * parameters and setup the CG solver from the CG factory which solves the
+   * linear system.
+   *
+   * @p executor The execution paradigm for the CG solver.
+   */
+  SolverCG(SolverControl &                solver_control,
+           std::shared_ptr<gko::Executor> executor,
+           std::shared_ptr<gko::LinOpFactory> preconditioner,
+           const AdditionalData &         data = AdditionalData());
   protected:
     /**
      * Store a copy of the settings for this particular solver.
diff --git a/source/lac/ginkgo_solver.cc b/source/lac/ginkgo_solver.cc
index 8223fc6a4d..2aa25a55ee 100644
--- a/source/lac/ginkgo_solver.cc
+++ b/source/lac/ginkgo_solver.cc
@@ -288,6 +288,19 @@ namespace GinkgoWrappers
       cg::build().with_criteria(this->combined_factory).on(executor);
   }
 
+  template <typename ValueType, typename IndexType>
+  SolverCG<ValueType, IndexType>::SolverCG(
+                                           SolverControl &                solver_control,
+                                           std::shared_ptr<gko::Executor> executor,
+                                           std::shared_ptr<gko::LinOpFactory> preconditioner,
+                                           const AdditionalData &         data)
+    : SolverBase<ValueType, IndexType>(solver_control, executor)
+    , additional_data(data)
+  {
+    using cg = gko::solver::Cg<ValueType>;
+    this->solver_gen =
+      cg::build().with_criteria(this->combined_factory).with_preconditioner(preconditioner).on(executor);
+  }
   // Explicit instantiations in GinkgoWrappers
 #  define DEALII_INSTANTIATE_FOR_EACH_VALUE_AND_INDEX_TYPE(_macro) \
     template _macro(float, int32_t);                               \
diff --git a/tests/ginkgo/solver.cc b/tests/ginkgo/solver.cc
index 560d9117c4..46deda45c8 100644
--- a/tests/ginkgo/solver.cc
+++ b/tests/ginkgo/solver.cc
@@ -57,11 +57,18 @@ main(int argc, char **argv)
     //                                                               gko::OmpExecutor::create());
     // std::shared_ptr<gko::Executor> exec = gko::OmpExecutor::create();
     std::shared_ptr<gko::Executor> exec = gko::ReferenceExecutor::create();
+    std::shared_ptr<gko::LinOpFactory> jacobi = gko::preconditioner::Jacobi<>::build().on(exec);
     GinkgoWrappers::SolverCG<>     solver(control, exec);
+    GinkgoWrappers::SolverCG<>     solver_with_jacobi_precond(control, exec, jacobi);
 
     check_solver_within_range(solver.solve(A, u, f),
                               control.last_step(),
                               35,
                               39);
+    u = 0.;
+    check_solver_within_range(solver_with_jacobi_precond.solve(A, u, f),
+                              control.last_step(),
+                              29,
+                              33);
   }
 }
diff --git a/tests/ginkgo/solver.output b/tests/ginkgo/solver.output
index 4ce62b0ef7..06d6d30d58 100644
--- a/tests/ginkgo/solver.output
+++ b/tests/ginkgo/solver.output
@@ -1,3 +1,4 @@
 
 DEAL::Size 32 Unknowns 961
 DEAL::Solver stopped within 35 - 39 iterations
+DEAL::Solver stopped within 29 - 33 iterations
-- 
2.39.5