Hi Andrew, The error indicates that one of the reweight card (actually the first one) is identical to original card. This is typically a mistake and therefore I made the code to crash in order that the user realize that. you can re-run the reweight by doing: ./bin/madevent reweight run_01 If the card are suppose to be different could you provide to me the param_card and reweight_card such that I can reproduce the problem? Cheers, Olivier On Dec 7, 2013, at 9:11 PM, Andrew Levin