Engine filename inconsistency...

Generally, I think that if you specify filename "X" to an engine in the writer-side Open() statement, you should also be able to specify "X" in the reader-side Open() statement and it should work. That is, an Engine should consider itself free to add a file-type suffix upon file creation, but if it does, it should be transparent to the user in that it should also add it on the reader side (assuming that it isn't already present). This isn't the way the BPfile engines work now. I.E.

Writer.Open("Filename.bp"); /* creates a file named "Filename.bp" / Writer.Close(); Reader.Open("Filename.bp"); / works. finds a file named "Filename.bp" */

Writer.Open("Filename"); /* automatically adds suffix .bp, creating "Filename.bp" / Writer.Close(); Reader.Open("Filename"); / fails to find Filename.bp */

So what's happening is that ADIOS2 is automatically adding the postfix on the writer side if it isn't already present, but not doing the same thing on the reader side. This makes it more awkward to switch engines because the reader code has to change.

Demonstrate by removing the ".bp" suffix from all the filenames in any BP test...