Problems when trying to display the values from a dataset

[jgalan]

I am having difficulties while printing the column data of the data frame defined inside the dataset.

The dataset is ready. You may now access the dataset using:

 - dSet->PrintMetadata()
 - dSet->GetDataFrame().GetColumnNames()
 - dSet->GetTree()->GetEntries()

root [0] ROOT::DisableImplicitMT()
root [1] dSet->GetDataFrame().Display({"final_posX"})->Print()
Error in <TRint::HandleTermInput()>: std::runtime_error caught: RLoopManager::Run: when the RDataFrame was constructed the number of slots required was 4, but when starting the event loop it was 1. Maybe DisableImplicitMT() was called after the RDataFrame was constructed?

Maybe @juanangp you got some insights on how to solve this?

[juanangp]

I think the issue is that the dataSet has been built with multiThreading enabled, looking at some ROOT forums there is not much to do while using Display with MT enabled.

I suggest the following:

• Make configurable to enable or disable MT at TRestDataSet::GenerateDataSet (default be enabled by default)
• Make configurable enable or disable MT at Import e.g. Import(const std::string& fileName, bool enableMT = true)

You should be able to do Display with a dataset which has been generated using MT enabled but it is imported with MT disabled.