User Program Restrictions under SCore

• SCore cluster system software is not sucure enough to be exposed to the internet. Place cluster(s) and related servers inside of a firewall.
  
  
• There is no way to specify an exact number of nodes for which user program to be allocated. Thus, it is not a good idea for a user program to assume a certain number of nodes to be allocated.
  
  
• Standard input (stdin) is not supported directly. Standard output (stdout) and standard error (stderr) are forwarded to the Front-End Process (FEP) (i.e. the scrun(1) command). If a user program requires standard input, combine the scatter command in a parallel job. See also scrun command man page for the parallel job.
  
  
• SIGQUIT is reserved for checkpointing. SIGCONT is reserved for gang scheduling.
  
  
• SCore users must have the same user ID and group IDs on all cluster hosts and on hosts where scrun is invoked.
  
  
• All environment variables at the time of the invocation of the scrun front-end process are copied to each cluster host on which the user parallel program will run.
  
  
• Do not attach a debugger to a user process running on a cluster host. Use the debug option and sc_inspectme() SCore-D system call instead.
  
  
• User program binary files must have read permission. This is so SCore-D can distribute the binary file to cluster hosts before invoking the user program on the cluster. Thus, users' binary files can exist on a local file system of a host where scrun is invoked.
  
  
• AFS, used as a network file system for a cluster wide file system, is not supported. This is because an AFS server may go down when a cluster consists of more than one hundred hosts. However, user program binary files can be located on an AFS file system.
  
  
• If the current directory of a user program is on an NFS file system, then core files may not be properly produced when two or more processes raise exceptions simultaneously. This is why automatic debugger attachment (the debug option) for exceptions is supported in MPC++ and MPICH-SCore.