COM4521/COM6521: Using ShARC (HPC)

This page documents how the ShARC HPC cluster can be used by COM4521/COM6521 students, this is predominantly to enable remote work on the assignment during the Easter break, however lab solutions are provided with a makefile which could be updated to work on HPC too.

This guide applies to ShARC which uses the SGE (Sun Grid Engine) scheduler, much of the guidance is not suitable for other university HPC systems such as Bessemer and Stanage as those use a difference scheduler.



Connecting to HPC has four requirements:

  1. University HPC Account
  2. Connected to the university VPN or on campus network
  3. University MFA
  4. SSH Client

Additionally, you will likely want to use a graphical SFTP (FTP over SSH) client to transfer files between your computer and the HPC system. Alternatively, scp can be used directly from your terminal or git can be used once logged into ShARC.

University HPC Account

To use university HPC you must first complete the HPC Driving License (VPN required), online training/test.

After completing the HPC Driving License notify me (r.chisholm(at), and I can request a HPC account on your behalf. It normally takes 1-2 working days for HPC accounts to be created and granted access to DCS private hardware.

University VPN

In order to connect to the HPC cluster you will either need to be connected to the university VPN or on the campus network (e.g. wifi). This is the same requirement as many other digital campus-only resources.

University MFA

HPC authentication uses the university’s multifactor authentication.

You will be prompted to enter a one-time code or send a push notification to your MFA device after entering your username and password. You should already have MFA setup, as it is now required for all university accounts and VPN access.

SSH Client

Typically Linux, MacOS and Windows (10+) all have ssh available via the command line. You may use other SSH clients if you have a preference.

SFTP Client

The below guide explains how to use FileZilla, a cross-platform graphical SFTP client.

Logging In

To login enter the following command in your terminal, replacing $USER with your university username e.g. acb12de.

ssh $

You will then be prompted to enter you password


On password confirmation you will be prompted to select a MFA option.

Either enter a passcode directly from the Duo mobile app, or enter 1 and respond to the push notification.

Duo two-factor login for $USER

Enter a passcode or select one of the following options:

 1. Duo Push to $PHONE_NUMBER

Passcode or option (1-1):

If login was successful you should see a success message and login welcome.

Success. Logging you in...
*         ShARC (Sheffield Advanced Research Computer) HPC cluster          *
*                       The University Of Sheffield                         *
*                                      *
*                                                                           *
*               Unauthorised use of this system is prohibited.              *

[$USER@sharc-login2 ~]$

Official HPC Connection Docs

Transferring Files

Download and install the FileZilla client from

When you first open FileZilla you need to create a site.

  • Select Site Manager from the menu bar: File -> Site Manager...
  • Click New site, and enter the name ShARC.
  • Enter the following properties in the right-hand panel:
    • General
      • Protocol: SFTP - SSH File Transfer Protocol
      • Host:
      • Logon Type: Interactive
      • User: Your username (e.g. acb12de)
    • Transfer Settings
      • Limit number of simultaneous connections: Should be ticked (true)
  • Now you can click Open to connect to ShARC.

When opening FileZilla in future, you can either select the ShARC site via the site-manager drop down (arrow next to the left-most icon in the icon bar), or reopen the site manager and double click ShARC to connect.

When you connect, the interactive logon prompt will open, this works the same as logging into SSH. First you will be requested to enter your password, followed by a Duo passcode or 1 to use a push notification.

Official HPC Transferring Files Docs

Your Assignment

The assignment handout code has been updated to include an updated Makefile and a directory scripts/sharc with job scripts you may want to use.

Official Using GPUs on ShARC Docs


Interactive Session

To compile your code on ShARC you must connect to an interactive session, interactive sessions do not have GPUs so can only be used for compilation.

You can request an interactive session with the qrshx command.

On success you should see the prompt change from @sharc-login to @sharc-node.

To leave the interactive session you can call exit.

[$USER@sharc-login2 ~]$ qrshx
[$USER@sharc-node009 ~]$ exit
[$USER@sharc-login2 ~]$ 

Loading Modules

Lots of software is installed on the HPC system, therefore to prevent conflicts it is necessary to manually load the required software.

module load libs/CUDA/11.6.0/binary
module load dev/gcc/8.2

If you add these 2 lines to .bashrc (in your home directory), they will be automatically loaded every time you login to ShARC. Otherwise you will need to call them manually after each login as required.

Building The Assignment

If you navigate to where you have uploaded your assignment code (e.g. cd com4521_assignment) you now be should be able to call make to compile your project. (Make sure you have updated the Makefile in the handout code.)

make will produce a Release build, if you wish to produce a Debug build (e.g. for additional validation checks) you should instead call make debug.

The output below is normal for compilation success, it merely shows the commands passed to the two compilers.

[$user@sharc-node009 com4521_assignment]$ make
nvcc -c -o build/release/src/ src/ -gencode arch=compute_35,code=sm_35 -gencode arch=compute_60,code=sm_60 -gencode arch=compute_60,code=compute_60 -I. -Isrc -Wno-deprecated-gpu-targets -lineinfo -O3 -DNDEBUG -Xcompiler -fopenmp -Xcompiler -I. -Xcompiler -Isrc -Xcompiler -Wall -Xcompiler -O3 -Xcompiler -DNDEBUG
gcc -c -o build/release/src/helper.c.o src/helper.c -fopenmp -I. -Isrc -Wall -O3 -DNDEBUG
gcc -c -o build/release/src/cpu.c.o src/cpu.c -fopenmp -I. -Isrc -Wall -O3 -DNDEBUG
gcc -c -o build/release/src/openmp.c.o src/openmp.c -fopenmp -I. -Isrc -Wall -O3 -DNDEBUG
nvcc -c -o build/release/src/ src/ -gencode arch=compute_35,code=sm_35 -gencode arch=compute_60,code=sm_60 -gencode arch=compute_60,code=compute_60 -I. -Isrc -Wno-deprecated-gpu-targets -lineinfo -O3 -DNDEBUG -Xcompiler -fopenmp -Xcompiler -I. -Xcompiler -Isrc -Xcompiler -Wall -Xcompiler -O3 -Xcompiler -DNDEBUG
nvcc -o bin/release/Particles build/release/src/ build/release/src/helper.c.o build/release/src/cpu.c.o build/release/src/openmp.c.o build/release/src/ -gencode arch=compute_35,code=sm_35 -gencode arch=compute_60,code=sm_60 -gencode arch=compute_60,code=compute_60 -I. -Isrc -Wno-deprecated-gpu-targets -lineinfo -O3 -DNDEBUG -Xcompiler -fopenmp -Xcompiler -I. -Xcompiler -Isrc -Xcompiler -Wall -Xcompiler -O3 -Xcompiler -DNDEBUG
[$user@sharc-node009 com4521_assignment]$

Errors and warnings take the below form. The exact messages may differ from those you receive in Visual Studio, but the code you are working with should remain cross-platform.

src/ error: expected a ";"


Note: These sample job scripts do NOT include commands to compile your project. You may have to wait for a batch job to run, so you don’t want it to fail due to compilation (see Compiling).

Two sample job scripts scripts/sharc/ and scripts/sharc/ have been provided for running your code. You will need to modify copies of these scripts to specify different runtime argument for your application.

The header of the job script contains a large number of parameters which can be modified to change things such as the requested job time, job name and email address to send job status updates to.

Note: The scheduler used (Sun Grid Engine) is unaware of GPUs, hence the number of GPUs requested is multiplied by the number of CPU cores requested. Therefore, you will find requesting more than 7 cores (the number of GPUs available) causes a job to queue indefinitely. Likewise, requesting 1 CPU core for non-OpenMP jobs should decrease queue times.

To submit the default job scripts call the desired command below from the root of your project:

qsub scripts/sharc/
qsub scripts/sharc/

You can then use qstat to check the status of your job.

Once your job has completed, two log files e.g will have been created. These contain the output and error streams from your job. You should check these to ensure that your job ran successfully and to recover any important output such as timing and validation data.

The sample run jobs should also output the image output_image.png which you can download to check.


In order to profile code on HPC it is necessary to submit a job to generate timeline and analysis files which can be imported into visual profiler.

It is necessary to install the Visual Profiler to view these outputs. It can be installed on a machine without an Nvidia GPU by using the command line silent flag (e.g. cuda_installer.exe -s visual_profiler_12.1 if using the CUDA 12.1 installer). Visual Profiler also requires the 64-bit Java Runtime Environment to be installed, otherwise it will fail at launch.

To submit the default profiling job script call the below command from the root of your project:

qsub scripts/sharc/

You can then use qstat to check the status of your job.

Once your job has completed, two log files e.g will have been created. These contain the output and error streams from your job. You should check these to ensure that your job ran successfully and to recover any important output such as timing and validation data.

Note: Profiling can be slow, therefore it’s possible the default 10 minute job time will be exceeded and the job will fail. This can be checked by running qstat -j <jobid> and checking the output’s exit_status to see whether it was killed.

The profiler will have created two output files timeline.nvprof and analysis.nvprof, you can download and import them into the Visual Profiler GUI.

  • File -> Import
  • Select Nvprof
  • Select Single process
  • Select timeline.nvvp for Timeline data file
  • Add analysis.nvprof to Event/Metric data files
  • Click Finish

CUDA Memory Checker

Compute sanitizer is available on HPC similar to the managed desktops, it can be executed with the sample job script to memory check Debug builds of your code. As before, you will need to modify a copy of this script to specify different runtime argument to your application.

qsub scripts/sharc/

On completion, Compute sanitizer’s output will be found in the two output files e.g


In order to interactively debug your code on HPC it is necessary to get an interactive GPU session. This will only be possible when there are free GPU nodes.

Note: gdb and cuda-gdb are complex and powerful applications, you may wish to attempt debugging with printf() first.

An interactive GPU session, can be requested with the below command:

qrshx -l gpu=1 -P rse -q rse-interactive.q

If this succeeds, and you have loaded the same two modules required for compilation, you should then be able to use cuda-gdb to interactively debug your application.

cuda-gdb --args "bin/debug/Particles" CUDA 100 512x512 output_image.png

Refer to the gdb and cuda-gdb documentation respectively (cuda-gdb is an extension of gdb so gdb information is transferable if you do not require the CUDA debugging features).

Contact Us

For queries relating to collaborating with the RSE team on projects:

Information and access to JADE II and Bede.

Join our mailing list so as to be notified when we advertise talks and workshops by subscribing to this Google Group.

Queries regarding free research computing support/guidance should be raised via our Code clinic or directed to the University IT helpdesk.