Which functions are collective operations? #4747
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https://adios2.readthedocs.io/en/v2.11.0/components/components.html#anatomy-of-an-adios-output says
https://adios2.readthedocs.io/en/v2.11.0/advice/advice.html mentions:
As far as I can tell, https://adios2.readthedocs.io/en/v2.11.0/engines/engines.html#supported-engines doesn't contain that information. Empirically it seems that at least |
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Replies: 1 comment 3 replies
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The docs are a little vague, in part because ADIOS still supports ongoing I/O research and there are special-purpose and experimental engines that may bend the rules. Such engines aren't as well documented as the more main-stream engines. For example the "inline" engine operates vastly differently than the others with no truly collective operations, but lots of things that have to happen cooperatively between the reader and the writer or things just don't work. Also, when new functionality like PerformDataWrite() is added to some engine (BP5 only), we've mostly just mentioned it where applicable. However, if you stick to the "must" list above, that should cover the mainstream engines. Strictly speaking BeginStep is often not actually collective (may not contain MPI operations), but since it must always be paired with an EndStep (which is collective in mainstream engines), considering it collective does no harm. Is there a specific situation you're interested in? |
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Thanks for the explanations. I think for my use case, I was mostly wondering about steps because, as far as I understand, that's the granularity where variables can change dimensionality. So it sounded logical to me that it's collective, but then I was confused by the "Advice" page not mentioning it. Maybe it would be good to update that page to include |
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Sure, open a PR. I'll have time to review. |
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For future reference, #4755 was just merged. |
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The docs are a little vague, in part because ADIOS still supports ongoing I/O research and there are special-purpose and experimental engines that may bend the rules. Such engines aren't as well documented as the more main-stream engines. For example the "inline" engine operates vastly differently than the others with no truly collective operations, but lots of things that have to happen cooperatively between the reader and the writer or things just don't work. Also, when new functionality like PerformDataWrite() is added to some engine (BP5 only), we've mostly just mentioned it where applicable. However, if you stick to the "must" list above, that should cover the mainstream engines. Str…