Platform LSF Administration Guide Version 6.2

Chapter 15
Specifying Resource Requirements
Administering Platform LSF
273
Span String
A span string specifies the locality of a parallel job. If span is omitted, LSF allocates the
required processors for the job from the available set of processors.
Syntax
Two kinds of span string are supported:
◆ span[hosts=1]
Indicates that all the processors allocated to this job must be on the same host.
◆ span[ptile=value]
Indicates the number of processors on each host that should be allocated to the job.
where value is:
❖ Default ptile value, specified by n processors. For example:
span[ptile=4]
The job requests 4 processors on each available host, regardless of how many
processors the host has.
❖ Predefined ptile value, specified by ’!’. For example:
span[ptile='!']
uses the predefined maximum job slot limit lsb.hosts (MXJ per host
type/model) as its value.
If the host or host type/model does not define MXJ, the default predefined
ptile value is 1.
❖ Predefined ptile value with optional multiple ptile values, per host type or
host model:
✧ For host type, you must specify same[type] in the resource requirement.
For example:
span[ptile='!',HP:8,SGI:8,LINUX:2] same[type]
The job requests 8 processors on a host of type HP or SGI, and 2
processors on a host of type
LINUX, and the predefined maximum job slot
limit in
lsb.hosts (MXJ) for other host types.
✧ For host model, you must specify same[model] in the resource
requirement. For example:
span[ptile='!',PC1133:4,PC233:2] same[model]
The job requests 4 processors on hosts of model PC1133, and 2 processors
on hosts of model PC233, and the predefined maximum job slot limit in
lsb.hosts (MXJ) for other host models.
See “Controlling Processor Allocation Across Hosts” on page 436 for more
information about specifying
span strings.