Feature #2812

Add metadata feature to automagically broadcast it

Added by Mark Miller 11 months ago. Updated 10 months ago.

Status:Pending Start:04/28/2017
Priority:Normal Due date:
Assigned to:- % Done:


Target version:-
Found in Version:2.12.1 OS:All
Impact:4 - High Support Group:Any
Expected Use:3 - Occasional


Until today, I hadn't realized that VisIt does indeed have the ability to broadcast a metadata object. This means a single rank in parallel can construct it and then broadcast it to all ranks in parallel. This is hugely convenient for dealing with parallel in most if not all database plugins. But, its a bit hidden from view. In fact, the only plugin that exploits it is Silo. I have been working with MOAB and Mili plugin developers dealing with this issue and we have always stumbled over the issue that its not easy to handle PopMD in parallel whilst being efficient in terms of filesystem interactions but keeping the algorithm simple.

I recommend the following to help ease development of db plugins for parallel...That VisIt automagically broadcast metadata (from rank 0) and only avert that if a plugin requests not to. This would be a new feature on metadata object. Call it the mdBcastRank. If set to -1, then its off. Otherwise, it specifies a rank to use as broadcaster and will do the broadcast just prior to return from call to PopMD in the avtFileFormat methods. We would have to touch many existing plugins to turn it off.

I rate this as high impact because it hugely simplifies db plugin development.


Updated by Eric Brugger 10 months ago

  • Status changed from New to Pending

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