I have implemented and committed (r18190) a new RMAPS module that sequentially maps ranks to the hosts listed in a hostfile. You must set -mca rmaps seq in order to access this module - it will -not- be selected any other way.
The basic method of operation respects the hostfile descriptions on the wiki page, but I will describe it here briefly as well: 1. if we are in a managed environment, we will only map to nodes within the allocation. If your hostfile contains nodes outside the allocation, we will report an error and abort. So if you want to map ranks sequentially, you need to be sure that the hostfile describing this mapping contains only hosts that -can- be mapped. In an unmanaged environment, we automatically include all the nodes in any specified hostfiles, so this won't be a problem. 2. if you specify a default-hostfile, we will use it - however, any hostfiles specified for an app_context will override the default-hostfile. Any apps that do -not- have a hostfile specified will be mapped sequentially to the hosts in the default-hostfile 3. if your app_context does not specify a number of procs, we will automatically map one proc to each and every entry in the hostfile 4. if your app_context does specify a number of procs, we will sequentially map that number of procs, one to each entry in the hostfile. Multiple app_contexts are supported, with the sequence continuing across the app_contexts. 5. if you specify a number of procs greater than the number of entries in your hostfile, we will map the overrun using byslot rules - i.e., we will start by filling the remaining slots on the first node in your hostfile, then proceed to fill the second node in your hostfile, etc. 6. if your allocation does not permit oversubscription, we will report an error and abort if you attempt to place more procs on a node than slots. Hope that helps Ralph
