NVidia Meeting 2015-3-4

Agenda

• Weds, March 4th, 1-5pm: VTK-m design review (Ken Moreland)
• Thurs, March 5th, 8am-noon: updates from NVIDIA

Design review

Issues raised in design review

How to handle multiple devices with one host?

We discussed the VTK-m strategy for supporting multiple devices from one host (i.e., a single node of Summit). Options presented were:

• one MPI task for each device (i.e., multiple MPI tasks per node)
  • minus: may be lots of MPI tasks
  • minus: may be incongruent with sim code's usage of MPI
  • minus: hard boundaries between devices
  • plus: easy to implement
• one MPI task per node, with (for example) threading to manage access to multiple devices
  • plus: less MPI tasks
  • plus: more likely to be congruent with sim code's usage of MPI
  • minus: hard boundaries between devices (??)
  • plus/minus: implementation easier? (depends on details)
• one MPI tasks per node, devices are treated as one giant device
  • plus: less MPI tasks
  • minus: could lend itself to inefficient patterns (reaching across device memories)
• one MPI task per node, devices are knowledgable of other devices and can coordinate between each other
  • plus: less MPI tasks
  • plus: more likely to be congruent with sim code's usage of MPI
  • plus: no boundaries between devices
  • minus: big implementation, right?