CS 475: Getting started on the ISTeC Cray

Access

Fill in the form cray account request in docx, or cray account request in pdf, or the the account request form, available on the Istec Cray website and send it to the Cray Systems manager Richard Casey (see the form).
You should have a reoplty back in about a week.

Follow the steps below for getting started on cray.

Access.
The hostname of cray is cray2.colostate.edu
To login in to cray using ssh enter the following command in the terminal:
```
		
  ssh "your-account-name"@cray2.colostate.edu
```
File Storage. The files in the home directory are backed up. Keep all your files there. To execute paralel program you need to be in the lustrefs directory. (You have one provided.) Also, Large files should be stored in lustrefs directory. Lustrefs is not backed up. It is best to store executables and their input output data in lustrefs, and copy anything valuable back to your home directory.
Transferring files from your computer onto CRAY home directory
Execute this command when you are logged into the CRAY.
```
  scp  "personnel-id"@pea.cs.colostate.edu:"file-path" . 
```
Compilers on the Cray.
The Cray user guide version 3 was used as reference for the information below. The default compiler loaded is the cray compiler. There are only a few licenses for this compiler, so we use the gcc compiler suite. Use the following command to swap to gcc
```
  module list
  module swap PrgEnv-cray PrgEnv-gnu
```
Use the Makefile to compile your codes.
Executing your program.
Move the code to your lustrefs directory, and execute it using the aprun command as follows:
```
  mv program lu*
  cd lu*
  aprun -n1 -d1 program
```
Check "man aprun" for aprun options. The -n option specifies the number of times (spawns) of "program". The -d option (used for openMP specifies the number of cores executing the code in a node. (each node consists of 24 cores: 4 processors each with 6 cores, memory, and interconnect).
Example of use: PA1 on the Cray
Here is the sequence of commands used, and here is the makefile. Here is a performance summary of running PA1 on the cray. Notice the difference in behavior as compared to the CS veggie machines.
Your job is to get a Cray account, and Take your own PA1 and run it on the Cray.