On January 2, 2018 we will be setting the default process mapping for the system OpenMPI installations on Argon to "map by socket". This is being done to improve the process distribution of jobs in the absence of any specific process mapping given at job submission time. This change will not require any action to be taken on your part. If you have any questions about this, contact firstname.lastname@example.org.
Related documentation for the Argon system is available here.