The SCore Single-User Environment

The figure below shows an example of the SCore single-user environment. Suppose that you have a cluster of eight compute hosts, i.e., comp0 through comp7, and a server host running the Cluster Database Server (scoreboard) and the Compute Host Lock Server (msgbserv).

Here is an example session to execute the hello command on the cluster using the scout environment:

	$ export SCBDSERV=server
	$ msgb -group pcc
	$ scout -g pcc
	SCOUT: Spawn done.
	SCOUT: session started
	$ scrun -nodes=8 ./hello
	SCORE: connected (jid=100)
	<0:0> SCORE: 8 hosts ready.
	Hello World! (from node 2)
	Hello World! (from node 5)
	Hello World! (from node 3)
	Hello World! (from node 6)
	Hello World! (from node 4)
	Hello World! (from node 7)
	Hello World! (from node 0)
	Hello World! (from node 1)
	$ exit
	SCOUT: session done
The procedure to execute hello is as follows:
  1. scout sends a message to the scoreboard daemon asking it for a list of compute hosts registered for the group.
  2. A request message is then sent to the msgbserv daemon asking it to reserve eight nodes for the exclusive use of the program. An acknowledgment message is sent back if all eight nodes can be reserved (no other SCore programs are currently using any of them)
  3. While msgbserv is locked scout spawns a control process called scremote on each of the compute nodes. The msgbserv lock is then released.
  4. When scrun is issued to execute the program, it requests scout to execute the program on 8 of the reserved compute hosts. scout then locks msgbserv and requests the scremote processes to fork and exec the scored operating system on the compute hosts on behalf of the user.
  5. Each scored process will then fork and exec the user's program which will execute until completion. When the program completes, the scored processes terminate and msgbserv is unlocked.
  6. When scout is exited, the msgbserv is again locked and the scremote processes are terminated. The msgbserv lock is finally released.
SCore Single-User Environment

It should be noted that other users can still use the cluster when the Compute Host Lock Server is not locked. Each time msgbserv is locked the blocks displayed in the msgb window will change to red and the user id of who locked the host, the time when the host was locked, and the host name are displayed in succession.

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$Id: env_single.html,v 1.2 2002/03/08 06:24:17 hirose Exp $