Platform LSF Administration Guide Version 6.2

Specifying a Mandatory First Execution Host
Administering Platform LSF
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Specifying a Mandatory First Execution Host
In general, the first execution host satisfies certain resource requirements that might not
be present on other available hosts.
LSF normally selects the first execution host dynamically according to the resource
availability and host load for a parallel job. You can also specify a mandatory first
execution host.
Specify a mandatory first execution host
Use an exclamation point (!) to indicate mandatory first execution host. You can specify
first execution host at job submission, or in the queue definition.
Job level
Use the -m option of bsub:
% bsub -n 32 -m "hostA! hostB hostC" myjob
hostA is the mandatory first execution host.
Queue level
Specify the first execution host in the list of hosts in the HOSTS parameter in lsb.queues:
HOSTS = hostA! hostB hostC
The queue-level specification of mandatory first execution host applies to all jobs
submitted to the queue.
Rules
The following rules apply when specifying first execution host:
◆ First execution host cannot be a host group or host partition, even if only one host
is in the group or partition. Jobs that specify a host group or host partition as first
execution host are rejected.
◆ The first execution host must satisfy the corresponding resource requirement
specified at submission or on the queue. The order string in the resource
requirement is ignored: the select, span and rusage strings in a resource requirement
apply to the first execution host but the order string does not.
If the specified first execution host does not satisfy the resource requirement, the
job will stay in the pending state until the resource requirement is satisfied.
◆ The first execution host can appear anywhere in the host string, but you can specify
only one first execution host.
If multiple first execution hosts are specified in HOSTS on a queue, only the first
valid first execution host is used, the others will be ignored as if they were not
specified.
◆ The keyword all is ignored if it is specified in the execution host list. The keyword
others is valid in the host list, but it cannot be the first execution host. Both
keywords are ignored if they are specified as the first execution host.
If the first execution host is incorrect at job submission, the job will be rejected. If
incorrect configurations exist on the queue level, warning messages will be logged and
displayed when LSF starts, restarts or is reconfigured.