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User Mailing

ICHEC mail #21

Posted: 2006-04-21

Dear ICHEC users,


1. First call for Class A applications
2. 2nd User Group Meeting
3. Scheduling policies, charging and accounting
4. Monitoring jobs' efficiency
5. Monthly reports
6. IAHPC workshop

1 – First call for Class A applications

ICHEC is now inviting proposals for Class A ("Grand Challenge") applications.

Class A applications will typically be submitted by consortia concerned with "Grand Challenge" problems, and are expected to yield high-impact scientific publications. These groups will require resources representing a substantial fraction of the centre's resources over a long period. As such, we only anticipate supporting a total of 7 such projects over the lifetime of the service.

Applicants considering applying for a Class A project are expected to have a good knowledge of the characteristics of the code(s) which they intend to use – such as scalability properties – before writing their proposal. For this reason, applicants who are not in such a position are advised to first apply for Class C access in order to undertake a basic scalability and performance study. Such an exercise is essential to provide an accurate estimate and a proper justification of the resources requested. If you intend to use packages supported by ICHEC, you may contact us via the helpdesk as we can assist you in this task.

Key characteristics of Class A project:

- Maximum duration: 24 months
- IBM 1350 cluster (Walton)
 - Compute resources: up to 650,000 CPU hours
 - Storage resources: up to 500 GB
- Bull NS6320 shared memory (Hamilton)
 - Compute resources: up to 40,000 CPU hours.
 - Storage resources: 100 GB

Applications will be peer-reviewed to international standards, and applicants will be notified of the outcome of their application within 8 weeks of the closing date. The deadline for application is Tuesday 2nd May, 9am.

Further information can be found at http://www.ichec.ie/full_national_service. A copy of the application guidelines can be found at http://www.ichec.ie/application_guidelines.

2 – 2nd User Group Meeting

The second ICHEC Users Group Meeting will take place on Tuesday 25th April 2006 (11am - 2pm), at the School of Cosmic Physics, Dublin Institute for Advanced Studies (DIAS) at 5 Merrion Square, Dublin 2. See http://www.dias.ie/index.php?section=general&subsection=findingus_merrion for more information on how to find it.


11.00 Welcome and Introduction

11.05 ICHEC status report
a/ hardware
b/ software
c/ utilisation and scheduling policies
d/ training and user support

11.45 ICHEC Report
a/ outcome from the HPC User survey
Recommendations for an improved National Service
Baseline procurement
Topical HPC Issues
b/ applying for resources to the Full National Service

12.15 tea/coffee break

12.40 Open discussion: user feedback

13.45 Session wrap-up
14.00 Close

Participation is also possible from NUIG via video-conferencing. For further information (e.g., location of the video conferencing facilities) please contact Grainne MacNamara at grainne.macnamara (Our e-mail addresses are formed by appending the suffix @ichec.ie).

This meeting is open to all ICHEC users, and participation is encouraged.

3 – Scheduling policies, charging and accounting

A fair share mechanism is now in place to ensure a fair access to resources to all users. Each job now has its priority derived from the following three criteria:

- the job's submission time (the longer a job has been queued, the higher its priority);
- the project's QoS (CosmoGrid, Class C and Class B);
- the historical usage of the system compared to the "target" allocation (jobs charged to projects which have already used more than their "fair share" are assigned lower priorities than those charged to projects which have underused their allocation).

Policies are under constant reviews, and rules will be tuned to ensure that all users have access to appropriate levels of resources while maximising usage of our systems.

We would like to remind all users that accounting will be turned on from 1st June. It is important to understand that the charging mechanism charges for resources allocated to each job, irrespective of the usage made of the resources. In other words, each job will be charged for the number of CPUs requested (irrespective of how many are actually used) * job's residency time (end date/time – start date/time). This policy is justified by the fact that resources allocated to specific jobs are unavailable to other users.

We therefore strongly encourage you to investigate the scalability and efficiency of your application before 1st June, to ensure that you get the most from resources allocated to your project. A number of commands (see following item) can assist you in this task.

From Monday 10th April, each batch submission script must now specify a valid project against which resources will be charged with the statement #PBS –A project_code (see User Mailings 18 and 20). A wrapper has been written to check that you have specified a valid project code at submission time. If in doubt, please contact us via the ICHEC helpdesk. Note also that unless you have joined a project supported as part of the Full National Service, your access to the facilities will be discontinued on 1st June. See http://www.ichec.ie/full_national_service and http://www.ichec.ie/application_guidelines for further instructions on how to apply to the full National Service.

Finally, we would like to request that all users who are not currently specifying sensible maximum runtimes in their PBS scripts start doing so. Specifying lower maximum runtimes result in faster turn around times (for your own jobs, and other users') thanks to the scheduler's backfill mechanism. PBS/Maui try to run the highest priority jobs first. When there are no longer sufficient resources to run the next highest priority job, Maui attempts to backfill jobs that are further down the priority list. It will only backfill jobs that will not affect the running of the top priority queued job. Jobs that require a small number of nodes and/or short amount of runtime are therefore likely to be backfilled more quickly than jobs requiring more resources.

4 - Monitoring jobs' efficiency

Users are encouraged to use the command "qutil" to investigate the performance of their running jobs.

Usage: qutil [ -u username | -j jobid,... | -a | -h ] [ -s ]

For instance:

qutil -a (shows all of your jobs)
qutil -j 5675,5677 (lists these two jobs with ID 5675 and 5677, but only if they belong to you)

You may also use the "pgprof" profiler for a more in-depth analysis of the performance of your application. See http://www.pgroup.com/doc/pgitools.pdf for further information about this tool.

5 – Monthly reports

Monthly reports describing our systems' availability and utilisation can be found at http://www.ichec.ie/reports. The March 2006 report is now available on-line.

6 – IAHPC workshop

The Irish Association for High-Performance Computing (IAHPC) will be holding a two day workshop on 8th - 9th June at the Tyndall Institute in Cork.

This meeting will include a series of presentations by HPC experts from EPCC and Daresbury Laboratories, so anyone with interest in HPC is warmly invited to take part in this event.

Further information will appear at www.iahpc.ie.

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