SCore PM vs Myricom GM

Myricom is a U.S company which produces the Myricom products such as the Myrinet PCI 64 bit 2Gbit cards and switches. Customers having Myrinet products installed can download both binaries and source code for Myricom's own network driver ("GM") and version of MPI (http://www.myri.com). Myrinet products are open architecture in the sense that Myricom provide information for anyone to write their own Myrinet drivers, and several drivers for Myrinet hardware have been produced independently of the Myricom GM driver. In particular the SCore Myrinet driver (called PM-myrinet) has been pre-eminent as being capable of outperforming Myricom's own driver over the years. Today the SCore PM-myrinet and Myricom's GM driver are roughly speaking of similar performance. The SCore PM driver still has the advantage of being capable of using a zero copy protocol, which means that users of SCore pm will see a greater bandwidth over Myrinet than do GM users.

The performance difference between GM and PM is not great and, at the date of writing this, Myricom will produce a zero copy capable driver to equal the PM driver quite soon.

Your Streamline-Computing PC cluster is installed with a modular kernel which makes moving from the SCore system installed to the Myricom GM system straightforward and can be carried out without a reboot providing no users are running jobs over Myrinet.

If you would like to convert your system to Myricom GM then please consult one of our technical staff, and read our other guide on Myricom GM clusters. However if you run Myricom GM your binaries compiled to run over Myrinet will not run over ethernet.

So why do we use SCore rather than Myricom GM ?

The principle reasons for adopting SCore are as following.

SCore is a complete parallel environment which has been developed over 10 years and is now mature. SCore has the following features:

• Installation tool for setting up cluster.
• The same binary can be run over any configured network (Myrinet, Ethernet, Gigabit, Shared memory).
• Time shared gang scheduler or batch scheduler available.
• Multiple compiler support for gnu,pgi.intel,kai,compaq,absoft, fujitsu,pghpf.
• Ability to easily add/delete compute nodes.
• Supports effective network trunking over ethernet (up to 400Mbits/s using multiple fast ethernet cards).
• Pre-emptive kernel level checkpointing.
• Runtime optimisation : mpi_zerocopy, mpi_eager can be turned on.
• Supports PVM over Myrinet.
• Support for running OpenMP jobs over Myrinet.

As far as we are aware Streamline Computing is the only UK company providing support for both Myricom GM and SCore based systems. We have a close relationship with both Myricom (we are one of only 2 UK Myricom resellers) and the SCore developers. SCore maintains a mailing list and is generally very fast to respond (next day, given the time difference of 9 hours between UK and Japan) should a problem arise. The SCore system is now maintained by an independent group of system developers producing GNU licensed software, but with links and support from Fujitsu, NEC and Compaq (Japan), among others.