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HFI consideration
The IBM Power 775 system that uses the HFI has more features for communication with
collective_groups and imm_send_buffers. The administrator must set the configuration
keyword SCHEDULE_BY_RESOURCES to include CollectiveGroups when
collective_groups are used.
collective_groups
The collective_groups requests the CAU groups for the specified protocol instances of the job
by using the following format:
Syntax: # @ collective_groups = number
The range of the collective_groups is 0 - 64. If the system is dedicated to your job, the value of
collective_groups is set to 64. If there are other jobs that run on the same nodes that are in
use, you reduce the setting so other jobs are able to use the nodes. You check the current
available collective_groups on the machine in the LoadLeveler cluster by using the
llstatus-R command, as shown in Example 2-20 on page 152. For more information, see
2.4.4, "Considerations for using CAU" on page 129.
imm_send_buffers
The imm_send_buffers requests a number of immediate send buffers for each window that is
allocated for each protocol instance of the job by using the following format:
Syntax: # @ imm_send_buffers=number
The value of the imm_send_buffers must be greater than or equal to zero, and it is inherited
from all the protocol instances of the job step unless the individual protocol instances are
specified with their own imm_send_buffers. For more information, see 2.4.1, "Considerations
for using HFI" on page 119.
Chapter 2. Application integration
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