Bump OPMD version and add delim

CMakeLists.txt

@@ -205,7 +205,7 @@ if (PARTHENON_ENABLE_OPENPMD)
   FetchContent_Declare(openPMD
     GIT_REPOSITORY "https://github.com/openPMD/openPMD-api.git"
     # we need newer than the latest 0.15.2 release to support writing attriutes from a subset of ranks
-    GIT_TAG        "bda3544") # develop as of 2024-07-12
+    GIT_TAG        "1c7d7ff") # develop as of 2024-09-02
   FetchContent_MakeAvailable(openPMD)
   install(TARGETS openPMD EXPORT parthenonTargets)
 endif()

src/outputs/parthenon_opmd.cpp

@@ -65,7 +65,8 @@ using namespace OutputUtils;
 
 template <typename T>
 void WriteAllParamsOfType(std::shared_ptr<StateDescriptor> pkg, openPMD::Iteration *it) {
-  const std::string prefix = "Params/" + pkg->label() + "/";
+  using OpenPMDUtils::delim;
+  const std::string prefix = "Params" + delim + pkg->label() + delim;
   const auto &params = pkg->AllParams();
   for (const auto &key : params.GetKeys()) {
     const auto type = params.GetType(key);

src/outputs/parthenon_opmd.hpp

@@ -20,6 +20,13 @@ namespace parthenon {
 
 namespace OpenPMDUtils {
 
+// Deliminter to separate packages and parameters in attributes.
+// More or less a workaround as the OpenPMD API does currently not expose
+// access to non-standard groups (such as "Params" versus the standard "meshes").
+// TODO(pgrete & reviewer) (agree on delim and add check for package name and keys) OR
+// better use of opmd-api
+inline static const std::string delim = "+";
+
 // Construct OpenPMD Mesh "record" name and comonnent identifier.
 // - comp_idx is a flattended index over all components of the vectors and tensors, i.e.,
 // the typical v,u,t indices.

src/outputs/restart_opmd.cpp

@@ -116,11 +116,20 @@ std::size_t RestartReaderOPMD::GetSwarmCounts(const std::string &swarm,
 
 template <typename T>
 void RestartReaderOPMD::ReadAllParamsOfType(const std::string &pkg_name, Params &params) {
+  using OpenPMDUtils::delim;
   for (const auto &key : params.GetKeys()) {
     const auto type = params.GetType(key);
     auto mutability = params.GetMutability(key);
     if (type == std::type_index(typeid(T)) && mutability == Params::Mutability::Restart) {
-      auto val = it->getAttribute("Params/" + pkg_name + "/" + key).get<T>();
+      auto attrs = it->attributes();
+      for (const auto & attr : attrs) {
+        std::cout << "Contains attribute: " << attr << std::endl;
+      }
+      std::cout << "Reading '"
+                << "Params" + delim + pkg_name + delim + key << "' with type: " << typeid(T).name()
+                << std::endl;
+
+      auto val = it->getAttribute("Params" + delim + pkg_name + delim + key).get<T>();
       params.Update(key, val);
     }
   }