Solved by ptrblck in post #4 
              
              
                If all devices are the same, use 
CUDA_VISIBLE_DEVICES=1,2 python script.py args 
to run the script and inside the script use cuda:0 and cuda:1 (or the equivalent .cuda(0), .cuda(1) commands). 
However, if the mapping is not what you expect via nvidia-smi, you could force the PCI bus order order via…