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From: Deborah Joanne Bard []
Sent: Friday, November 22, 2013 7:18 PM
To: Todd Martinez
Cc: Marshall, Stuart L.; Adesanya, Adeyemi; Abel, Tom; Kaehler, Ralf; Brian Moritz; Thomas Peter Devereaux; Eriksson, Thomas; Voss, Johannes; O'Grady, Christopher P.; Perazzo, Amedeo; Gaponenko, Igor; Radmer, Randall James; Ho, Ling Cherd; Hoeche, Stefan; Dubois, Richard; Boehnlein, Amber; Luitz, Steffen; Gruber, Shirley; Yan, Jun; van den Bedem, Henry
Subject: Re: GPU computing at SLAC: meeting 22nd Nov 2pm

Hi All,

  the minutes of today's meeting are below. Please let me know if you have any comments or suggestions!






attending: Tom Abel,  Yemi Adesanya, Debbie Bard, Stefan Hoeche, Igor Gaponenko, Stuart Marshall.


Summary: There is demand for a small central GPU resource, where

users can practice and develop code and run small-scale analyses. It is

likely that there is not demand for a larger facility. It is also likely

that the affordable option of an interactive/batch server using desktop

GPUs would be sufficient to meet the needs of users, but there are

drawbacks to such a scheme. We will prepare a proposal outlining the use

cases for such a resource, with input from groups across slac.


Here's an outline of our discussions:

- How are people using GPUs at SLAC right now?


Kipac: the KIPAC GPU cluster is used mostly by individuals using GPUs for

analysis work on small/medium scales. Visualisation group has their own GPUs.


LCLS: Three GPUs are currently used by individual users with a specific code base.


- Do existing GPU users have an interest in using central GPU resources?

What kind of demand is there (among existing and potential GPU users) for

this kind of resource?


Kipac: There is some interest in further small-scale use of GPUs for

processing/fitting data.


LCLS: Users in LCLS do not have full access to SLAC resources, so they are

unlikely to use central resources. Only pre=processing, filtering etc is

done at SLAC, otherwise the user typically takes data back to the home

institution for analysis. However, a configurable workflow is being

developed which may include GPU modules.


Theory: Potential to use GPUs for event generation. This is a large code

that would have to be re-written for the GPU, as yet it's unclear whether

this is worth it in terms of possible speed-up, and in terms of end user

resources. A central GPU resource would help scope out the possible gains.


- What kind of resources are useful to people now? What would be useful to the wider SLAC community?


Yemi: There's already demand from groups (Kipac, theory, SIMES) for

resources to try out GPU implementation  without investing in the hardware



Igor: there are plenty of libraries/tools for GPUs, perhaps we could bring

some in and set them up.


- What problems do we need to be aware of (e.g. over-subscribed interactive nodes)?


Yemi: New LSF protocol manages access to GPU slots in exclusive process

mode, so a clash of resources is avoided. However, this won't work for

interactive nodes and is not an efficient use of CPU/GPU.


Tom: It may be better to invest in consumer-grade GPUs that don't have the

capacity/[precision, but are sufficient for user needs. 1/10th price!


Igor: Have to be careful about the precision, and whether memory will be

sufficient. Need a good, fast connection to where the data is stored!


Stuart: Can't fit consumer GPUs into a regular server farm. Need to

consider options there.


Igor: remember NVidia/cuda is not he only game in town! OpenCL/ATI GPUs

may be a good option.


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