Add Support for Reading MPI Partitioning From File

This commit introduces new, experimental support for loading a
partitioning of the cells from a text file.  The name of the file is
passed into the simulator using the new, hidden, command line option

    --external-partition=filename

and we perform some basic checking that the number of elements in the
partition matches the number of cells in the CpGrid object.

ebos/eclbasevanguard.hh

@@ -119,6 +119,12 @@ struct ZoltanParams {
     using type = UndefinedProperty;
 };
 
+template <class TypeTag, class MyTypeTag>
+struct ExternalPartition
+{
+    using type = UndefinedProperty;
+};
+
 template<class TypeTag, class MyTypeTag>
 struct AllowDistributedWells {
     using type = UndefinedProperty;
@@ -179,6 +185,12 @@ struct ZoltanParams<TypeTag,TTag::EclBaseVanguard> {
     static constexpr auto value = "graph";
 };
 
+template <class TypeTag>
+struct ExternalPartition<TypeTag, TTag::EclBaseVanguard>
+{
+    static constexpr auto* value = "";
+};
+
 template<class TypeTag>
 struct AllowDistributedWells<TypeTag, TTag::EclBaseVanguard> {
     static constexpr bool value = false;
@@ -268,6 +280,12 @@ public:
                              "See https://sandialabs.github.io/Zoltan/ug_html/ug.html "
                              "for available Zoltan options.");
         EWOMS_HIDE_PARAM(TypeTag, ZoltanParams);
+        EWOMS_REGISTER_PARAM(TypeTag, std::string, ExternalPartition,
+                             "Name of file from which to load an externally generated "
+                             "partitioning of the model's active cells for MPI "
+                             "distribution purposes. If empty, the built-in partitioning "
+                             "method will be employed.");
+        EWOMS_HIDE_PARAM(TypeTag, ExternalPartition);
 #endif
         EWOMS_REGISTER_PARAM(TypeTag, bool, AllowDistributedWells,
                              "Allow the perforations of a well to be distributed to interior of multiple processes");
@@ -297,6 +315,7 @@ public:
         serialPartitioning_ = EWOMS_GET_PARAM(TypeTag, bool, SerialPartitioning);
         zoltanImbalanceTol_ = EWOMS_GET_PARAM(TypeTag, double, ZoltanImbalanceTol);
         zoltanParams_ = EWOMS_GET_PARAM(TypeTag, std::string, ZoltanParams);
+        externalPartitionFile_ = EWOMS_GET_PARAM(TypeTag, std::string, ExternalPartition);
 #endif
         enableDistributedWells_ = EWOMS_GET_PARAM(TypeTag, bool, AllowDistributedWells);
         ignoredKeywords_ = EWOMS_GET_PARAM(TypeTag, std::string, IgnoreKeywords);

ebos/eclcpgridvanguard.hh

@@ -38,11 +38,58 @@
 #include <opm/models/blackoil/blackoilproperties.hh>
 
 #include <array>
+#include <filesystem>
+#include <fstream>
 #include <functional>
+#include <iterator>
 #include <memory>
+#include <stdexcept>
 #include <tuple>
 #include <vector>
 
+#include <fmt/format.h>
+
+#if HAVE_MPI
+
+namespace Opm { namespace details {
+    class MPIPartitionFromFile
+    {
+    public:
+        explicit MPIPartitionFromFile(const std::filesystem::path& partitionFile)
+            : partitionFile_(partitionFile)
+        {}
+
+        std::vector<int> operator()(const Dune::CpGrid& grid) const;
+
+    private:
+        std::filesystem::path partitionFile_{};
+    };
+
+    inline std::vector<int>
+    MPIPartitionFromFile::operator()(const Dune::CpGrid& grid) const
+    {
+        std::ifstream pfile { this->partitionFile_ };
+
+        auto partition = std::vector<int> {
+            std::istream_iterator<int> { pfile },
+            std::istream_iterator<int> {}
+        };
+
+        if (partition.size() != static_cast<std::vector<int>::size_type>(grid.size(0))) {
+            throw std::invalid_argument {
+                fmt::format("Partition file '{}' with {} values does "
+                            "not match CpGrid instance with {} cells",
+                            this->partitionFile_.generic_string(),
+                            partition.size(), grid.size(0))
+            };
+        }
+
+        return partition;
+    }
+}} // namespace Opm::details
+
+#endif // HAVE_MPI
+
 namespace Opm {
 template <class TypeTag>
 class EclCpGridVanguard;
@@ -224,6 +271,12 @@ public:
     void loadBalance()
     {
 #if HAVE_MPI
+        if (const auto& extPFile = this->externalPartitionFile();
+            !extPFile.empty() && (extPFile != "none"))
+        {
+            this->setExternalLoadBalancer(details::MPIPartitionFromFile { extPFile });
+        }
+
         this->doLoadBalance_(this->edgeWeightsMethod(), this->ownersFirst(),
                              this->serialPartitioning(), this->enableDistributedWells(),
                              this->zoltanImbalanceTol(), this->gridView(),

ebos/eclgenericcpgridvanguard.cc

@@ -52,6 +52,7 @@
 #include <ebos/femcpgridcompat.hh>
 #endif //HAVE_DUNE_FEM
 
+#include <algorithm>
 #include <cassert>
 #include <numeric>
 #include <optional>

ebos/eclgenericvanguard.hh

@@ -228,6 +228,11 @@ public:
      */
     double zoltanImbalanceTol() const
     { return zoltanImbalanceTol_; }
+
+    const std::string& externalPartitionFile() const
+    {
+        return this->externalPartitionFile_;
+    }
 #endif
 
     /*!
@@ -292,6 +297,7 @@ protected:
     bool serialPartitioning_;
     double zoltanImbalanceTol_;
     std::string zoltanParams_;
+    std::string externalPartitionFile_{};
 #endif
     bool enableDistributedWells_;
     std::string ignoredKeywords_;

opm/simulators/flow/SimulatorFullyImplicitBlackoilEbos.hpp

@@ -97,7 +97,6 @@ struct LoadFile
     using type = UndefinedProperty;
 };
 
-
 template<class TypeTag>
 struct EnableTerminalOutput<TypeTag, TTag::EclFlowProblem> {
     static constexpr bool value = true;
@@ -135,7 +134,6 @@ struct LoadFile<TypeTag, TTag::EclFlowProblem>
     static constexpr auto* value = "";
 };
 
-
 template <class TypeTag>
 struct LoadStep<TypeTag, TTag::EclFlowProblem>
 {