The MadGraph interface is prepared to run generation of events performed by MadGraph
n times until the desired number of events that the user requests to Gauss is met.
MadGraph is only prepared to handle seeds up to 30081*30081 and hence it can only run up to 30081 separate times. This way, using as input seed the Gauss
RunNumber the internal MadGraph seed is calculated as:
(RunNumber - 1) * (MaxRuns) + (number of runs) + 1
In the interface
MaxRuns is set to 30081, the actual maximum value MadGraph can handle. This implies that
RunNumber values that are usually set in productions (~17e6) not only produce seeds bigger than what MadGraph can handle, but it causes the integer that represents the seed to overflow into a negative value, which results in catastrophic behaviour.
In reality, the adaptor is already setup so that ideally MadGraph would only be run once by using the DecFile efficiency which must be correctly set. This MR proposes to set
MaxRuns to 10 to account for possible corner cases or DecFiles that are not correctly setup. This way
RunNumbers used in productions result in seeds that MadGraph can handle.