Walk Me Through
This is a "quick start" introduction into using the BA-HPC cluster at the Bibliotheca Alexandrina. This covers the general activities most users will deal with when using the cluster.
In order to properly follow this quick start guide, you should have
- an account on BA-HPC cluster
- an account at our support system
- knowledge on how to use
- a basic familiarity with Unix
If do not have an account, you could follow the above links before proceeding with this quick start.
2. Logging into the login node
The cluster have a node available for users to log into. From this node you can submit and monitor your jobs, look at results of the jobs, etc.
- DO NOT RUN computationally intensive processes on the login node. Maximum runtime of any process on login node is 30 minutes.
- On login node, maximum simultaneous processes for each user is 100.
Note that your home directory
$HOMEis limited to 100 MB. Use
datadirectory (linked at $HOME/data) for large data.
For most tasks you will wish to accomplish, you will start by logging into the login node. In order to do that, you
need to use the Secure Shell protocol (SSH). This is standardly installed as ssh on Unix systems, and clients are
available for Windows and Mac. If you are using a non-Unix system like Windows, you must install
an SSH client.
On Unix-like systems, you can login by executing
ssh -i path/to/private/key firstname.lastname@example.org in the terminal. If you're using
BitVise client, you need to set the host to hpc.bibalex.org, Initial method to public
key and port to 22.
- Note that you'll need to use your real username instead of
3. Setting up your environment modules
The software environment used on BA-HPC cluster can be managed via modules. Modules facilitate the task of updating applications and provide a user-controllable mechanism for accessing software revisions and controlling combination of versions. For the job to executed, you must load any required modules before submitting your job.
Common commands to work with modules:
module avail # lists available modules module list # lists current loaded modules module help module-name # help on specific module module whatis module-name # brief description on a specific module module display module-name # display changes by a given module module load module-name # load a specific module module unload module-name # unloads a specific module module clear # unloads all loaded modules
module loadmultiple versions of the same module at the same time (including same version for different compilers). The module command will report a conflict if you attempt to do so.
4. Submitting parallel jobs
To handle the queuing, scheduling, and execution of jobs the BA-HPC cluster use a batch scheduling
system called Slurm (Simple Linux Utility for Resource Management). Normally, you will submit jobs by writing a job script file and
submitting the job to Slurm with the
sbatch command takes a number of options (some of which can be omitted or defaulted). These options define various
requirements of the job, which are used by the scheduler to figure out what is needed to run your job, and to schedule
it to run as soon as possible, subject to the constraints on the system, usage policies, and considering the other
users of the cluster.
The options to
sbatch can be given on the command line, or in most cases inside the job script. When given inside the
job script, the option is placed alone on a line starting with
#SBATCH (you must include a space after the
#SBATCH lines SHOULD come before any non-comment/non-blank line in the script.
Choosing a Queue
On the BA-HPC cluster, you only specify a partition when you want to run your job on a GPU enabled nodes.
To request GPUs for your job on the HPC, you need to add the
#SBATCH --gres=gpu:N options to your job script file, where N specifies the number of
GPUs that you are requesting. Kindly note that we have at most 2 GPUs per node and the total number
of GPU enabled nodes is 16.
Currently, we do not directly charge usage of GPUs. GPU based jobs usage will charged for the CPUs they consume on the GPU enabled node.Every GPU enabled node have 2 GPUs and 16 CPU cores. Since all jobs run in exclusive mode, consuming 1 GPU resource will also consume 8 CPU cores.
5. Creating and submitting MPI job
The Message Passing Interface (MPI) is a standardized and portable system for communication between the various tasks of parallized jobs in HPC environments. A number of different implementations of MPI libraries are available at our cluster. Although the MPI interface itself is somewhat standardized, the different versions are not binary compatible. It is important that you match the MPI implementation you use and with which your code was compiled. The recommended MPI library on BA-HPC cluster is Intel MPI libraries.
Let's start by compiling a sample MPI program written in C. The program initialize a defined number
of processes that print the 'Hello World' line to a file along with process rank.
The source code for this program can be found at this
To start using MPI environment, load the intel impi module using:
[username@login01 ~] module load impi
Let's use our newly loaded module to compile our C program, using MPI C compiler wrapper
[username@login01 ~] mpicc hello-mpi.c -o hello-mpi.bin
Now that we got our binary file, let's create a job script to submit it to OGS.
Here's an example of a simple script that will specify the necessary job parameters, we'll call it
#! /bin/bash #SBATCH --job-name=mpi_job #SBATCH --ntasks=24 #SBATCH --cpus-per-task=1 mpirun -np 24 ./hello-mpi.bin
#SBATCH --job-name=mpi_jobspecify the job name.
#SBATCH --ntasks=24restart the job in the case the system has a crash or is rebooted.
#SBATCH --cpus-per-task=1specifies the number of cores per task, we will need only one core per process.
mpirun -np 24 ./hello-mpi.binrun the MPI executable and specifies number of processes.
Now that you have a job script, you need to submit the job to the cluster with the
command. Make sure the Intel MPI libraries are loaded first then use 'sbatch' to submit the job
to the scheduler
[username@login01 ~] module list Currently Loaded Modulefiles: 1) GCCcore/5.4.0 2) binutils/2.26-GCCcore-5.4.0 3) icc/2016.3.210-GCC-5.4.0-2.26 4) ifort/2016.3.210-GCC-5.4.0-2.26 5) iccifort/2016.3.210-GCC-5.4.0-2.26 6) impi/18.104.22.168-iccifort-2016.3.210-GCC-5.4.0-2.26 [username@login01 ~] sbatch hello-mpi.sh Submitted batch job 156
At this point, your job has been placed in the queue, and will wait its turn for resources to be available. Depending on how heavily used the cluster is at that time, and how many resources you are requesting, your job might start within minutes or it might wait for hours.
Once resources become available, our scheduler will assign resources to your job, including one or more nodes.
The standard output and standard error streams will be directed to a file, by default
in the directory where you started the job, where the
is the job number as described above.
Output from your job can be viewed in the above specified file shortly after it starts running (assuming it has output something). This can be used to check the status of your job, although it is recommended make your code generates a lot of output to redirect it to another file.
For our trivial example from the last section, when the job completes we should see something like
[username@login01]$ cat slurm-156.output Hello world: rank 12 of 24 running on comp085.local Hello world: rank 1 of 24 running on comp085.local Hello world: rank 2 of 24 running on comp085.local Hello world: rank 4 of 24 running on comp085.local Hello world: rank 7 of 24 running on comp085.local Hello world: rank 8 of 24 running on comp085.local Hello world: rank 9 of 24 running on comp085.local Hello world: rank 14 of 24 running on comp085.local Hello world: rank 15 of 24 running on comp085.local Hello world: rank 16 of 24 running on comp085.local Hello world: rank 17 of 24 running on comp085.local Hello world: rank 18 of 24 running on comp085.local Hello world: rank 20 of 24 running on comp085.local Hello world: rank 21 of 24 running on comp085.local Hello world: rank 0 of 24 running on comp085.local Hello world: rank 3 of 24 running on comp085.local Hello world: rank 5 of 24 running on comp085.local Hello world: rank 6 of 24 running on comp085.local Hello world: rank 10 of 24 running on comp085.local Hello world: rank 11 of 24 running on comp085.local Hello world: rank 13 of 24 running on comp085.local Hello world: rank 19 of 24 running on comp085.local Hello world: rank 22 of 24 running on comp085.local Hello world: rank 23 of 24 running on comp085.local
As you can see in the output files above, the MPI program executed and each process was assigned a unique rank, which was printed off along with the hostname.
6. Creating and submitting CUDA job
CUDA is a parallel computing platform and API model created by Nvidia. It allows you to use a CUDA-enabled GPU for general purpose processing – an approach termed GPGPU (General-Purpose computing on Graphics Processing Units). The CUDA platform is a software layer that gives direct access to the GPU's virtual instruction set and parallel computational elements, for the execution of compute kernels.
Again let's start by compiling a sample CUDA program written in C. The program use GPU to add two 2
vectors of integers in parallel. It starts by generating 2 vectors of size
n then pass
these vectors to the GPU memory, after that we make each core simply sums a single element from
each of the two input vectors and writes the result into the output vector. Finally, we print only
m number of elements into the output file. The source code for this program can be
found at this github gist
. To start using the CUDA library, let's load Intel C compiler and CUDA
[username@login01 ~] module load icc CUDA
Then let's use the loaded Nvidia CUDA Compiler (NVCC) to compile our source code
[username@login01 ~] nvcc vector-add.cu -o vector-add.bin
An example of a simple script that will specify the necessary job parameters for a GPU based job,
we'll call it
#!/bin/bash #SBATCH --job-name=first-cuda-job #SBATCH --partition=gpu #SBATCH --gres=gpu:1 #SBATCH --nodes=1 #SBATCH --ntasks=1 ./vector-add.bin 100000 10
There's some additional options we've put in our job script:
#SBATCH --partition=gpuSubmit the job to the gpu partition.
#SBATCH --gres=gpu:1Specify the number of GPUs. In this example we only need one GPU card.
#SBATCH --nodes=1Specify the number of required nodes. In this example we only need one node.
#SBATCH --ntasks=1Specify the number of CPU cores/process to be used. In this example we only need one process to initiate our program execution on the GPU. Maximum number of CPU cores/process to be used is 16.
./vector-add.bin 100000 10Generate two vectors of length 100000, and print only the first 10 elements in the output file.
Now that you have a job script, let's submit the job to the cluster. Make sure the CUDA library are loaded first then use 'sbatch' to submit the job to the scheduler
[username@login01 ~] module list Currently Loaded Modulefiles: 1) CUDA/8.0.44 [username@login01 ~] sbatch cuda-vec_add.sh Submitted batch job 157
After the job completes, we should see something like
[username@login01]$ cat slurm-157.out h_x = 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 h_y = 100000.0 99999.0 99998.0 99997.0 99996.0 99995.0 99994.0 99993.0 99992.0 99991.0 The sum is: 100001.0 100001.0 100001.0 100001.0 100001.0 100001.0 100001.0 100001.0 100001.0 100001.0
7. Monitoring job status
The basic command for monitoring your jobs' status is the
command. Because normally you are only interested in your jobs, it is advisable to add the
flags, to speed up the command and only show your jobs. Replace
with your username.