Remove a dependency in writing VTU files.

Previously, one of the lambda functions that write parts updated a variable outside
the lambda function that was later checked. This works when running everything
sequentially, but introduces a race condition when we want to run things
in parallel. Move the updating code out of the lambda function, and so
effectively make it 'const' in the sense that it no longer writes into
variables outside of the lambda function.

diff --git a/source/base/data_out_base.cc b/source/base/data_out_base.cc
index f0c05d94845b335c5fa3079a36d09379e6c2b073..e303b1bfc7194442718552ae1af5626f82acf865 100644 (file)
--- a/source/base/data_out_base.cc
+++ b/source/base/data_out_base.cc
@@ -6494,7 +6494,6 @@ namespace DataOutBase
     // place
     const Table<2, float> data_vectors =
       std::move(*create_global_data_table_task.return_value());
-    std::vector<bool> data_set_written(n_data_sets, false);
 
     // then write data.  the 'POINT_DATA' means: node data (as opposed to cell
     // data, which we do not support explicitly here). all following data sets
@@ -6502,7 +6501,6 @@ namespace DataOutBase
     out << "  <PointData Scalars=\"scalars\">\n";
 
     const auto stringize_nonscalar_data_range = [&flags,
-                                                 &data_set_written,
                                                  &data_names,
                                                  &data_vectors,
                                                  ascii_or_binary,
@@ -6539,10 +6537,6 @@ namespace DataOutBase
                         "in VTK/VTU format."));
         }
 
-      // mark these components as already written:
-      for (unsigned int i = first_component; i <= last_component; ++i)
-        data_set_written[i] = true;
-
       // write the header. concatenate all the component names with double
       // underscores unless a vector name has been specified
       o << "    <DataArray type=\"Float32\" Name=\"";
@@ -6691,14 +6685,21 @@ namespace DataOutBase
 
 
     // When writing, first write out all vector and tensor data
+    std::vector<bool> data_set_handled(n_data_sets, false);
     for (const auto &range : nonscalar_data_ranges)
       {
+        // Mark these components as already handled:
+        const auto first_component = std::get<0>(range);
+        const auto last_component  = std::get<1>(range);
+        for (unsigned int i = first_component; i <= last_component; ++i)
+          data_set_handled[i] = true;
+
         out << stringize_nonscalar_data_range(range);
       }
 
     // Now do the left over scalar data sets
     for (unsigned int data_set = 0; data_set < n_data_sets; ++data_set)
-      if (data_set_written[data_set] == false)
+      if (data_set_handled[data_set] == false)
         {
           out << stringize_scalar_data_set(data_set);
         }