Give each thread using vtk a separate runtime device tracker

vtkm/cont/RuntimeDeviceTracker.cxx

@@ -29,7 +29,10 @@
 #include <vtkm/cont/tbb/DeviceAdapterTBB.h>
 
 #include <algorithm>
+#include <map>
+#include <mutex>
 #include <sstream>
+#include <thread>
 
 #define VTKM_MAX_DEVICE_ADAPTER_ID 8
 
@@ -155,8 +158,22 @@ void RuntimeDeviceTracker::ForceDeviceImpl(vtkm::cont::DeviceAdapterId deviceId,
 VTKM_CONT
 vtkm::cont::RuntimeDeviceTracker GetGlobalRuntimeDeviceTracker()
 {
-  static vtkm::cont::RuntimeDeviceTracker globalTracker;
-  return globalTracker;
+  static std::mutex mtx;
+  static std::map<std::thread::id, vtkm::cont::RuntimeDeviceTracker> globalTrackers;
+  std::thread::id this_id = std::this_thread::get_id();
+
+  std::unique_lock<std::mutex> lock(mtx);
+  auto iter = globalTrackers.find(this_id);
+  if (iter != globalTrackers.end())
+  {
+    return iter->second;
+  }
+  else
+  {
+    vtkm::cont::RuntimeDeviceTracker tracker;
+    globalTrackers[this_id] = tracker;
+    return tracker;
+  }
 }
 }
 } // namespace vtkm::cont

vtkm/cont/RuntimeDeviceTracker.h

@@ -207,13 +207,13 @@ private:
                        bool runtimeExists);
 };
 
-/// \brief Get the global \c RuntimeDeviceTracker.
+/// \brief Get the \c RuntimeDeviceTracker for the current thread.
 ///
 /// Many features in VTK-m will attempt to run algorithms on the "best
 /// available device." This often is determined at runtime as failures in
 /// one device are recorded and that device is disabled. To prevent having
-/// to check over and over again, VTK-m features generally use the global
-/// device adapter so that these choices are marked and shared.
+/// to check over and over again, VTK-m uses per thread runtime device tracker
+/// so that these choices are marked and shared.
 ///
 VTKM_CONT_EXPORT
 VTKM_CONT