GWU cluster (Corcoran Hall)

Some information about the old cluster can be found at here.

The cluster has been updated: it is now a cluster with 16 nodes each with 2 GPUs for a total of 32 GPUs (gtx480s). These cards have 1.5 GB of memory and deliver for dslash about 50GFlops/s in double precision and 125 GFlops/s in single precision (see Ben's Performance benchmarks).

The interconnects are still 4x DDR infiniband which provides 5Gb/s x 4lanes = 20Gb/s (signaling) which due to 8/10 encoding translates to a 16Gb/s=2GB/s in each direction (for more Infinband details consult wikipedia page).

The scheduling system on the cluster is Sun Grid Engine (sge). For infiniband we have installed OFED and openmpi (v1.5) and mvapich2 (v1.5.1). We prefer to use openmpi since it provides tight integration with the scheduler (the mpi processes get killed when you delete a job from the scheduler). A simple script is given below:

#$ -S /bin/csh
#$ -cwd
#$ -j y
#$ -o job_output.log$JOB_ID
##$ -q all.q@@node
#$ -q all.q@@gpu
#$ -l gpu_count=1
#$ -pe openmpi 8
#$ -l h_rt = 01:30:00

mpirun -n $NSLOTS --mca btl_openib_flags 1 test_dslash_multi_gpu < check.in >& output_np${NSLOTS}.log

Note that if your job consumes gpus you should use -l gpu_count=1 (one gpu per process) and you should also include --mca btl_openib_flags 1 flag to make sure that openmpi and cuda work together. If you only use the cpu codes, the flag is not necessary. Note that the new nodes are in the all.q queue and you should use all.q@@gpu if you want to use them or all.q@@node if you want to use the old nodes.

Queue admin

Disable/enable nodes

If you want to reboot a node while there are pending jobs in the queue, you should disable it from the queue first:

qmod -d \*@gpu05

disables node gpu05 from all the queues. Note that we need to escape * so that the shell doesn't expand it. Once the node is rebooted, we need to reenable the node using

qmod -e \*@gpu05

Setting up pe's

To add/remove/modify a pe use qconf. For example qconf -spl shows you all available pe's and qconf -sp openmpi shows you the configuration of openmpi pe. To modify it, use qconf -mp openmpi. The important parameters to configure are start_proc_args and end_proc_args which allow you to do a pre/post execution setup and allocation_rule which can be either $round_robin or $fill_up.