Subsetting Data for in situ visualization

[MuzafarWani]

I want to know can ADIOS handle a scenario where ADIOS is used for in situ visualization and a mesh is defined for a variable and visualization happens for x time steps out of N time steps for one variable of a simulation, After few time steps I don't want to transfer the whole variable for visualization only a part of that variable, as only certain part of the variable has changed in between the time steps.
Can it be done with ADIOS

[pnorbert]

The simple answer to your question is yes.

Caveat: ADIOS is not doing the in situ visualization, it only transfers the data requested by the consumer (reader) who performs the visualization. It entirely depends on the consumer what data is requested and therefore, transferred, in each step.

I suggest you look at examples/hello/sstWriter/sstWriter.py and examples/hello/sstReader/sstReader.py example and tinker with the loop in the reader to make decisions what you want to pull from the writer in each step. Let us know if you can't get it working the way you want it.

My question is however, how does the reader know what parts of the variable has changed? ADIOS has no functions to remember the data from previous steps and to compare it to the current data, and indicate somehow what has changed since the last step. So you would need to perform this comparison in your producer code and add this information as extra variables into the ADIOS output stream, which the consumer can read first and then request data accordingly.

[pnorbert]

Oh, I just realize you opened an issue on the ADIOS repo. This has been replaced by the ADIOS2 repo for many years now. I hope you are using ADIOS2 by now. https://github.com/ornladios/ADIOS2

[MuzafarWani]

Okay got the basic idea.