check engine type

[liangwang0734]

Hi, in the C++ interface, what is the routine to find out the engine type?

PS: In my case, I set the engine to BP5 for my output in the XML file but got an error that shows BP4Writer::EndStep is called.
(I've checked the validity of the XML file by setting the engine in the XML file to an invalid value like BPx and then it gives an error, indicating that the XML file is indeed picked up).

The debug trace relevant to adios2 can be found here.

[eisenhauer]

The Engine::Type() method returns what you want:

 * From ADIOS2 engine type: "bpfile", "sst", "dataman", "insitumpi", "hdf5"
 * @return engine type as lower case string
 */
std::string Type() const;

[eisenhauer]

(I'm not sure what to think about the trace, but lets take this one step at a time...)

[liangwang0734]

Thanks @eisenhauer That helped me a lot!

And, it turned out that the engine type in our test DOES change during the simulation.

Sorry that I don't have a minimum example yet to reproduce the problem; but my understanding of our code is that we store an and adios2::IO object io_ and an adios2::Engine object engine_ in a class.
When doing an output with the io_name_, say, "checkpoint", we do the following

• io_ = ad.DeclareIO(io_name_)
• engine_ = io_.open(filename, mode)
• when done, call engine_.Close() and ad_.RemoveIO(io_name_)

It appears to me that only the first iteration gets the correct engine type from the XML file. The subsequent iterations fall back to the default BP4.

I wonder if this is due to some lifetime logic in adios2? Note that in our case, for different checkpoint filenames, the io_name_ is the same ("checkpoint"), thus we declared and removed io instances of the same io_name_ repeatedly.

[liangwang0734]

I'll make another issue for the change of engine issue. So closing this one.

[liangwang0734]

@eisenhauer sorry, a follow-up question: is the following way to set and check engine/parameters correct:

  io_ = ad.DeclareIO(io_name_);
  io_.SetEngine("BP5");
  io_.SetParameter("SubStreams", "0");
  auto params = io_.Parameters();
  std::cout << "Substreams = " << params["SubStreams"] << std::endl;

[eisenhauer]

Sorry for the delayed response, but yes, that's the right way to set and check engine parameters.