Fixes for opening an iteration

include/openPMD/IO/AbstractIOHandler.hpp

@@ -61,7 +61,11 @@ class unsupported_data_error : public std::runtime_error
  * @brief Determine what items should be flushed upon Series::flush()
  *
  */
+#ifdef __NVCOMPILER_MAJOR__
+enum class FlushLevel
+#else
 enum class FlushLevel : unsigned char
+#endif
 {
     /**
      * Flush operation that was triggered by user code.
@@ -84,7 +88,11 @@ enum class FlushLevel : unsigned char
      * CREATE_DATASET tasks.
      * Attributes may or may not be flushed yet.
      */
-    SkeletonOnly
+    SkeletonOnly,
+    /**
+     * Only creates/opens files, nothing more
+     */
+    CreateOrOpenFiles
 };
 
 namespace internal

include/openPMD/Iteration.hpp

@@ -72,6 +72,7 @@ namespace internal
          * containing this iteration.
          */
         std::string filename;
+        bool beginStep = false;
     };
 
     class IterationData : public AttributableData
@@ -249,14 +250,16 @@ class Iteration : public Attributable
     void flush(internal::FlushParams const &);
     void deferParseAccess(internal::DeferredParseAccess);
     /*
-     * Control flow for read(), readFileBased(), readGroupBased() and
-     * read_impl():
-     * read() is called as the entry point. File-based and group-based
+     * Control flow for runDeferredParseAccess(), readFileBased(),
+     * readGroupBased() and read_impl():
+     * runDeferredParseAccess() is called as the entry point.
+     * File-based and group-based
      * iteration layouts need to be parsed slightly differently:
      * In file-based iteration layout, each iteration's file also contains
      * attributes for the /data group. In group-based layout, those have
      * already been parsed during opening of the Series.
-     * Hence, read() will call either readFileBased() or readGroupBased() to
+     * Hence, runDeferredParseAccess() will call either readFileBased() or
+     * readGroupBased() to
      * allow for those different control flows.
      * Finally, read_impl() is called which contains the common parsing
      * logic for an iteration.
@@ -265,10 +268,10 @@ class Iteration : public Attributable
      * Calling it on an Iteration not yet parsed is an error.
      *
      */
-    void read();
     void reread(std::string const &path);
-    void readFileBased(std::string filePath, std::string const &groupPath);
-    void readGorVBased(std::string const &groupPath);
+    void readFileBased(
+        std::string filePath, std::string const &groupPath, bool beginStep);
+    void readGorVBased(std::string const &groupPath, bool beginStep);
     void read_impl(std::string const &groupPath);
 
     /**
@@ -278,7 +281,7 @@ class Iteration : public Attributable
      *
      * @return AdvanceStatus
      */
-    AdvanceStatus beginStep();
+    AdvanceStatus beginStep(bool reread);
 
     /**
      * @brief End an IO step on the IO file (or file-like object)

include/openPMD/backend/Writable.hpp

@@ -119,11 +119,11 @@ OPENPMD_private
      * These members need to be shared pointers since distinct instances of
      * Writable may share them.
      */
-    std::shared_ptr<AbstractFilePosition> abstractFilePosition;
-    std::shared_ptr<AbstractIOHandler> IOHandler;
-    internal::AttributableData *attributable;
-    Writable *parent;
-    bool dirty;
+    std::shared_ptr<AbstractFilePosition> abstractFilePosition = nullptr;
+    std::shared_ptr<AbstractIOHandler> IOHandler = nullptr;
+    internal::AttributableData *attributable = nullptr;
+    Writable *parent = nullptr;
+    bool dirty = true;
     /**
      * If parent is not null, then this is a vector of keys such that:
      * &(*parent)[key_1]...[key_n] == this
@@ -146,6 +146,6 @@ OPENPMD_private
      * Writable and its meaning within the current dataset.
      *
      */
-    bool written;
+    bool written = false;
 };
 } // namespace openPMD

src/IO/ADIOS/ADIOS2IOHandler.cpp

@@ -2652,6 +2652,7 @@ namespace detail
 
         case FlushLevel::InternalFlush:
         case FlushLevel::SkeletonOnly:
+        case FlushLevel::CreateOrOpenFiles:
             /*
              * Tasks have been given to ADIOS2, but we don't flush them
              * yet. So, move everything to m_alreadyEnqueued to avoid

src/Iteration.cpp

@@ -148,13 +148,12 @@ Iteration &Iteration::open()
     if (it.m_closed == CloseStatus::ParseAccessDeferred)
     {
         it.m_closed = CloseStatus::Open;
+        runDeferredParseAccess();
     }
-    runDeferredParseAccess();
     Series s = retrieveSeries();
     // figure out my iteration number
     auto begin = s.indexOf(*this);
     s.openIteration(begin->first, *this);
-    // @todo, maybe collective here
     IOHandler()->flush(internal::defaultFlushParams);
     return *this;
 }
@@ -238,7 +237,16 @@ void Iteration::flushFileBased(
         s.openIteration(i, *this);
     }
 
-    flush(flushParams);
+    switch (flushParams.flushLevel)
+    {
+    case FlushLevel::CreateOrOpenFiles:
+        break;
+    case FlushLevel::SkeletonOnly:
+    case FlushLevel::InternalFlush:
+    case FlushLevel::UserFlush:
+        flush(flushParams);
+        break;
+    }
 }
 
 void Iteration::flushGroupBased(
@@ -252,7 +260,16 @@ void Iteration::flushGroupBased(
         IOHandler()->enqueue(IOTask(this, pCreate));
     }
 
-    flush(flushParams);
+    switch (flushParams.flushLevel)
+    {
+    case FlushLevel::CreateOrOpenFiles:
+        break;
+    case FlushLevel::SkeletonOnly:
+    case FlushLevel::InternalFlush:
+    case FlushLevel::UserFlush:
+        flush(flushParams);
+        break;
+    }
 }
 
 void Iteration::flushVariableBased(
@@ -267,7 +284,16 @@ void Iteration::flushVariableBased(
         this->setAttribute("snapshot", i);
     }
 
-    flush(flushParams);
+    switch (flushParams.flushLevel)
+    {
+    case FlushLevel::CreateOrOpenFiles:
+        break;
+    case FlushLevel::SkeletonOnly:
+    case FlushLevel::InternalFlush:
+    case FlushLevel::UserFlush:
+        flush(flushParams);
+        break;
+    }
 }
 
 void Iteration::flush(internal::FlushParams const &flushParams)
@@ -327,26 +353,6 @@ void Iteration::deferParseAccess(DeferredParseAccess dr)
         std::make_optional<DeferredParseAccess>(std::move(dr));
 }
 
-void Iteration::read()
-{
-    auto &it = get();
-    if (!it.m_deferredParseAccess.has_value())
-    {
-        return;
-    }
-    auto const &deferred = it.m_deferredParseAccess.value();
-    if (deferred.fileBased)
-    {
-        readFileBased(deferred.filename, deferred.path);
-    }
-    else
-    {
-        readGorVBased(deferred.path);
-    }
-    // reset this thing
-    it.m_deferredParseAccess = std::optional<DeferredParseAccess>();
-}
-
 void Iteration::reread(std::string const &path)
 {
     if (get().m_deferredParseAccess.has_value())
@@ -359,18 +365,31 @@ void Iteration::reread(std::string const &path)
 }
 
 void Iteration::readFileBased(
-    std::string filePath, std::string const &groupPath)
+    std::string filePath, std::string const &groupPath, bool doBeginStep)
 {
+    if (doBeginStep)
+    {
+        /*
+         * beginStep() must take care to open files
+         */
+        beginStep(/* reread = */ false);
+    }
     auto series = retrieveSeries();
 
     series.readOneIterationFileBased(filePath);
 
     read_impl(groupPath);
 }
 
-void Iteration::readGorVBased(std::string const &groupPath)
+void Iteration::readGorVBased(std::string const &groupPath, bool doBeginStep)
 {
-
+    if (doBeginStep)
+    {
+        /*
+         * beginStep() must take care to open files
+         */
+        beginStep(/* reread = */ false);
+    }
     read_impl(groupPath);
 }
 
@@ -540,7 +559,7 @@ void Iteration::read_impl(std::string const &groupPath)
     readAttributes(ReadMode::FullyReread);
 }
 
-AdvanceStatus Iteration::beginStep()
+AdvanceStatus Iteration::beginStep(bool reread)
 {
     using IE = IterationEncoding;
     auto series = retrieveSeries();
@@ -565,7 +584,8 @@ AdvanceStatus Iteration::beginStep()
     }
 
     // re-read -> new datasets might be available
-    if ((series.iterationEncoding() == IE::groupBased ||
+    if (reread &&
+        (series.iterationEncoding() == IE::groupBased ||
          series.iterationEncoding() == IE::variableBased) &&
         (this->IOHandler()->m_frontendAccess == Access::READ_ONLY ||
          this->IOHandler()->m_frontendAccess == Access::READ_WRITE))
@@ -679,18 +699,37 @@ void Iteration::runDeferredParseAccess()
     {
         return;
     }
+
+    auto &it = get();
+    if (!it.m_deferredParseAccess.has_value())
+    {
+        return;
+    }
+    auto const &deferred = it.m_deferredParseAccess.value();
+
     auto oldAccess = IOHandler()->m_frontendAccess;
     auto newAccess = const_cast<Access *>(&IOHandler()->m_frontendAccess);
     *newAccess = Access::READ_WRITE;
     try
     {
-        read();
+        if (deferred.fileBased)
+        {
+            readFileBased(deferred.filename, deferred.path, deferred.beginStep);
+        }
+        else
+        {
+            readGorVBased(deferred.path, deferred.beginStep);
+        }
     }
     catch (...)
     {
+        // reset this thing
+        it.m_deferredParseAccess = std::optional<DeferredParseAccess>();
         *newAccess = oldAccess;
         throw;
     }
+    // reset this thing
+    it.m_deferredParseAccess = std::optional<DeferredParseAccess>();
     *newAccess = oldAccess;
 }
 

src/ReadIterations.cpp

@@ -63,7 +63,7 @@ SeriesIterator::SeriesIterator(Series series) : m_series(std::move(series))
              * the step after parsing the file is ok.
              */
             openIteration();
-            status = it->second.beginStep();
+            status = it->second.beginStep(/* reread = */ true);
             break;
         case IterationEncoding::groupBased:
         case IterationEncoding::variableBased:
@@ -72,7 +72,7 @@ SeriesIterator::SeriesIterator(Series series) : m_series(std::move(series))
              * access to the file until now. Better to begin a step right away,
              * otherwise we might get another step's data.
              */
-            status = it->second.beginStep();
+            status = it->second.beginStep(/* reread = */ true);
             openIteration();
             break;
         }
@@ -107,7 +107,8 @@ SeriesIterator &SeriesIterator::operator++()
     case IE::variableBased: {
         // since we are in group-based iteration layout, it does not
         // matter which iteration we begin a step upon
-        AdvanceStatus status = currentIteration.beginStep();
+        AdvanceStatus status{};
+        status = currentIteration.beginStep(/* reread = */ true);
         if (status == AdvanceStatus::OVER)
         {
             *this = end();
@@ -142,7 +143,8 @@ SeriesIterator &SeriesIterator::operator++()
         using IE = IterationEncoding;
     case IE::fileBased: {
         auto &iteration = series.iterations[m_currentIteration];
-        AdvanceStatus status = iteration.beginStep();
+        AdvanceStatus status{};
+        status = iteration.beginStep(/* reread = */ true);
         if (status == AdvanceStatus::OVER)
         {
             *this = end();