The man page for numactl states the following: 
 
       --preferred=node 
              Preferably allocate memory on node, but if memory  cannot  be 
              allocated  there fall back to other nodes.  This option takes 
              only a single node number. 
 
And indeed when invoking numactl with --preferred=1-3, the preferred node is 
set to 1.  However, no warning/error is issued to notify the user that the 
invocation as such was incorrect.  Adding a check and informing the user would 
be nice.