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{{:FAQ: Programming and Debugging}}
{{:FAQ: Programming and Debugging}}
== Getting Help ==
{{:FAQ: Getting Help}}
=== I have encountered a problem while using a SHARCNET system and need help, who should I talk to? ===
If you have access to the Internet, we encourage you to use the [ problem ticketing system] (described in detail [[Knowledge_Base# SHARCNET Problem Ticket System|below]]) through the [ web portal].  This is the most efficient way of reporting a problem as it minimizes email traffic and will likely result in you receiving a faster response than through other channels.
You are also welcome to contact system administrators and/or high performance technical computing consultants at any time. You may find their contact information on the [ directory] page.
=== How long should I expect to wait for support? ===
Unfortunately SHARCNET does not have adequate funding to provide support 24 hours a day, 7 days a week.  User support and system monitoring is limited to regular business hours: there is no official support on weekends or holidays, or outside 9:00 - 17:00 EST . 
Please note that this includes monitoring of our systems and operations, so typically when there are problems overnight or on weekends/holidays system notices will not be posted until the next business day. 
=== SHARCNET Problem Ticket System ===
==== What is a "problem ticket system"? ====
This is a system that allows anyone with a SHARCNET account to start a persistent email thread that is referred to as a "problem ticket".  The thread is stored indefinitely by SHARCNET and can be consulted by any SHARCNET user in the future.  When a user submits a new ticket it will be brought to the attention of an appropriate and available SHARCNET staff member for resolution. 
You can find the SHARCNET ticket system [ here], or by logging into our website and clicking on "Help" then "Problems" in the top left-hand-side menu.
==== How do I search for existing tickets ? ====
Type a meaningful string into the <i>search box</i> when logged into the SHARCNET web portal.  You can find this text entry box beside the <i>Go</i> button on the top right-hand-side of the page in the web portal. 
It is recommended that one use specific words when searching, for example the exit code returned in your job output, or the error message produced when attempting a command. Use of common search terms may produce too many results and this coupled with the lack of sophisticated ranking for results means your search will likely be misleading or time consuming if you have to sift through many results by hand.
==== What do I need to specify in a ticket ? ====
If you do not find any tickets that deal with you current problem ([[Knowledge_Base# How do I search for existing tickets ? |as illustrated above]]) then you should ensure you include the following information, if relevant, when [[Knowledge_Base# How do I submit a ticket?|submitting a ticket]]:
#use a concise and unique <i>Subject</i> for the ticket
#*this makes it easier to identify in search results, for example
#select sensible values for the <i>System Name</i> and <i>Category</i> drop down boxes
#*this helps guide your ticket to the right staff member as quickly as possible
#in the <i>Comment</i> text entry box:
##if the problem pertains to a job report the <u>jobid</u> associated with the job
##*this is an integer that is returned by sqsub when you submit the job
##*you can also find a listing of your recent jobs (including their jobid) in the web portal [ at the bottom of this page]
##report the exact commands necessary to duplicate the problem, as well as any error output that helps identify the problem
##*if relevant, this should include how the code is compiled, how the job is submitted, and/or anything else you are doing from the command line relating to the problem
##if this ticket relates to another ticket, please specify the associated ticket number(s)
##if you'd like for a particular staff member to be aware of the ticket, mention them
#if you want to expedite resolution you can [[Knowledge_Base#How do I give other users access to my files ? |make your files publicly available]] ahead of time 
#*you should include any relevant files required to duplicate the problem
#*if you're not comfortable with changing your own file permissions, in <i>Comment</i> you can request that a staff member provide a location where you can copy the necessary files, or arrange file transfer via other means.  If your code is really sensitive you may have to arrange to meet in person to show them the problem.
==== How do I submit a ticket? ====
We recommend that you read the above section on [[Knowledge_Base#What do I need to specify in a ticket ? |what to specify in a ticket]] before submitting a new ticket.
Users can [ submit a problem ticket] describing an issue, problem or other request and they will then receive messages concerning the ticket via email (the ticket can also be consulted [ via the web portal]).
You can also open a ticket automatically by emailing <i></i> with the email address associated with your SHARCNET account.
=== How do I give other users access to my files ? ===
There are two ways to provide other users with access to your files.  The first is by changing the file attributes of your directories directly with the chmod command and the second is by using file access control lists (acl). Using ACLs is more flexible as it allows you to specify individual users and groups and their respective privileges, whereas using chmod is more coarse grained and only allows you to set the permissions for your group and global access.  At present ACLs are only supported on the SHARCNET global work (/work) and home (/home) filesystems.
====providing global access with chmod====
The following instructions provide commands that you can use to make your files available to all SHARCNET users, including staff.  It assumes that you are sharing files in your <i>/home</i> directory, but you can change this to <i>/work</i> or <i>/scratch</i> or etc. with the same effect.
In the below, instead of <your-subdirectory> , type the name of the subdirectory where the files you want to give access to are located:
(1) Go to your home directory by running:
(2) Authorize access to the home directory by running:
        chmod o+x  .
(3) Authorize access to <your-subdirectory> by running:
        chmod -R o+rX <your-subdirectory>
Note that if the directory you wish to share is nested multiple directories below your home directory (eg. you want to give access to ~/dir1/dir2, but not ~/dir1) you will have to run:
        chmod o+x .
in any of the intervening directories if they are not already globally accessible.
To restrict all public access due to these changes one can simply run the following commands:
        chmod o-x .
====providing per-user/group access with setfacl====
An Access Control List (ACL) is basically a list of users and groups with their associated file access privileges which is associated with a file/directory.  At present ACLs are only supported on the SHARCNET global work (/work) and home (/home) filesystems.
One can see the ACL for a particular file/directory with the '''getfacl''' command, eg.
[sn_user@hnd50 ~]$ getfacl /work/sn_user
getfacl: Removing leading '/' from absolute path names
# file: work/sn_user
# owner: sn_user
# group: sn_user
One uses the '''setfacl''' command to modify the ACL for a file/directory.  To add read and execute permissions for this directory for user ricky, eg.
[sn_user@hnd50 ~]$ setfacl -m u:ricky:rx /work/sn_user
Now there is an entry for ''user:ricky'' with ''r-x'' permissions:
[sn_user@hnd50 ~]$ getfacl /work/sn_user
getfacl: Removing leading '/' from absolute path names
# file: work/sn_user
# owner: sn_user
# group: sn_user
To remove an ACL entry one uses the '''setfacl''' command with the '''-x''' argument, eg.
[sn_user@hnd50 ~]$ setfacl -x u:ricky /work/sn_user
Now there is no longer an entry for ''ricky'':
[sn_user@hnd50 ~]$ getfacl /work/sn_user
getfacl: Removing leading '/' from absolute path names
# file: work/sn_user
# owner: sn_user
# group: sn_user
Note that if one wants to provide access to a nested directory then the permissions need to be changed on all the parent directories using the ''-R'' flag.  Please see the man pages for these commands ''man getfacl; man setfacl'' for further information. If you'd like help utilizing ACLs please [ email].
=== I am new to parallel programming, where can I find quick references at SHARCNET? ===
SHARCNET has a number of training modules on parallel programming using MPI, OpenMP, pthreads and other frameworks.  Each of these modules has working examples that are designed to be easy to understand while illustrating basic concepts.  You may find these along with copies of slides from related presentations and links to external resources on the [[Main Page]] of this training/help site.
=== I am new to parallel programming, can you help me get started with my project? ===
Absolutely. We will be glad to help you from planning the project, architecting your application programs with appropriate algorithms and choosing efficient tools to solve associated numerical problems to debugging and analyzing your code. We will do our best to help you speed up research.
=== Can you install a package on a cluster for me? ===
Certainly.  We suggest you make the request by sending e-mail to [], or [ opening a problem ticket] with the specific request.
=== I am in a process of purchasing computer equipment for my research, would you be able to provide technical advice on that? ===
If you tell us what you want, we may be able to help you out.
=== Does SHARCNET have a mailing list or user group? ===
Yes. You may subscribe to one or more mailing lists on the email list page available once you log into the web portal. To find it, please go to MyAccount - Settings - Details in the menu bar on the left and then click on Mail on the "details" page. Don't forget to save your selections.
=== Does SHARCNET provide any training on programming and using the systems? ===
Yes. SHARCNET provides workshops on specific topics from time to time and offers courses at some sites. Every June, SHARCNET holds an annual ''summer school'' with a variety of in-depth, hands-on workshops.  All materials from past workshops/presentations can be found on the SHARCNET web portal.
=== How do I watch tickets I don't own? ===
There are two ways.  First, to view the tickets of user "USERID", type the URL like below:
,where USERID is the user you want to see. In the "Actions" column, click on "watch" for problems that you want to follow. This should enable you to receive notifications if any of the problems you are "watching" are updated.
If you want to do the same thing for tickets posted by other members in your group, just access their userpage (listed on )
The other way is to use 'search box' in the SHARCNET website. By typing the ticket number or userid, you can do similar thing described above.
== Research at SHARCNET ==
== Research at SHARCNET ==

Revision as of 15:02, 22 September 2014

Sharcnet logo.jpg
Knowledge Base / Expanded FAQ

This page is a comprehensive collection of essential information needed to use SHARCNET, gathered conveniently on a single page of our Help Wiki. If you are a new SHARCNET user, this page most likely contains all you need to get going on SHARCNET. However, there is much more information in this Help Wiki. Please use the search box to find pages that may be relevant to you. You can also go to the Main Page of this wiki for a general table of contents. Finally, you can also look at the list of all articles in this Help Wiki or a list of all categories.




SHARCNET stands for Shared Hierarchical Academic Research Computing Network. Established in 2000, SHARCNET is the largest high performance computing consortium in Canada, involving 19 universities and colleges across southern, central and northern Ontario.

SHARCNET is a member consortium in the Compute/Calcul Canada national HPC platform.

Where is SHARCNET?

The main office of SHARCNET is located in the Western Science Centre at The University of Western Ontario.

What does SHARCNET have?

The primary SHARCNET compute system is Graham heterogeneous cluster located at the University of Waterloo. It is named after Wes Graham, the first director of the Computing Centre at Waterloo. It consists of 41,548 cores and 520 GPU devices, spread across 1,185 nodes of different configurations.

What can I do with SHARCNET?

If you have a program that takes months to run on your PC, you could probably run it within a few hours using hundreds of processors on SHARCNET / Compute Canada clusters, provided your program is inherently parallelisable. If you have hundreds or thousands of test cases to run through on your PC or computers in your lab, then with hundreds of processors running those cases independently will significantly reduce your test cycles.

Who is running SHARCNET?

The daily operation and development of SHARCNET computational facilities is managed by a group of highly qualified system administrators. In addition, we have a team of high performance technical computing consultants, who are responsible for technical support on libraries, programming and application analysis.

How do I contact SHARCNET?

For technical inquiries, you may send E-mail to or, or contact your local system administrator or HPC specialist. For general inquiries, you may contact the SHARCNET main office.

Getting an Account with SHARCNET and Related Issues

To use SHARCNET (and also Compute Canada) facilities one has to apply for a Compute Canada account.

Logging in to Systems, Transferring and Editing Files

How do I login to SHARCNET?

You access the SHARCNET clusters using ssh. For Graham and other national systems Compute Canada credentials are required. For the remaining systems, listed here, you will require SHARCNET credentials.

Unix/Linux/OS X

To login to a system, you need to use an Secure Shell (SSH) connection. If you are logging in from a UNIX-based machine, make sure it has an SSH client (ssh) installed (this is almost always the case on UNIX/Linux/OS X). If you have the same login name on both your local system and SHARCNET, and you want to login to, say, graham, you may use the command:


If your Compute Canada username is different from the username on your local systems, then you may use either of the following forms:

ssh -l username

If you want to establish an X window connection so that you can use graphics applications such as gvim and xemacs, you can add a -Y to the command:

ssh -Y

This will automatically set the X DISPLAY variable when you login.


If you are logging from a computer running Windows and need some pointers we recommend consulting our SSH tutorial.

What is the difference between Login Nodes and Compute Nodes?

Login Nodes

Most of our clusters have distinct login nodes associated with them that you are automatically redirected to when you login to the cluster (some systems are directly logged into, eg. SMPs and smaller specialty systems). You can use these to do most of your work preparing for jobs (compiling, editing configuration files) and other low-intensity tasks like moving and copying files.

You can also use them for other quick tasks, like simple post-processing, but any significant work should be submitted as a job to the compute nodes. On most login nodes, each process is limited to 1 cpu-hour; this will be noticable if you perform anything compute-intensive, and can affect IO-oriented activity as well (such as very large scp or rsync operations.)

How can I suspend and resume my session?

The program screen can start persistent terminals from which you can detach and reattach. The simplest use of screen is

screen -dR

which will either reattach you to any existing session or create a new one if one doesn't exist. To terminate the current screen session, type exit. To detach manually (you are automatically detached if the connection is lost) press ctrl+a followed by d, you can the resume later as above (ideal for running background jobs). Note that ctrl+a is screen's escape sequence, so you have to do ctrl+a followed by a to get the regular effect of pressing ctrl+a inside a screen session (e.g., moving the cursor to the start of the line in a shell).

For a list of other ctrl+a key sequences, press ctrl+a followed by ?. For further details and command line options, see the screen manual (or type man screen on any of the clusters).

Other notes:

  • If you want to create additional "text windows", use Ctrl-A Ctrl-C. Remember to type "exit" to close it.
  • To switch to a "text window" with a certain number, use Ctrl-A # (where # is 0 to 9).
  • To see a list of window numbers use Ctrl-A w
  • To be presented a list of windows and select one to use, use Ctrl-A " (This is handy if you've made too many windows.)
  • If the program running in a screen "text window" refuses to die (i.e., it needs to be killed) you can use Ctrl-A K
  • For brief help on keystrokes use Ctrl-A ?
  • For extensive help, run "man screen".

What operating systems are supported?

UNIX in general. Currently, Linux is the only operating system used within SHARCNET.

What makes a cluster different than my UNIX workstation?

If you are familiar with UNIX, then using a cluster is not much different from using a workstation. When you login to a cluster, you in fact only log in to one of the cluster nodes. In most cases, each cluster node is a physical machine, usually a server class machine, with one or several CPUs, that is more or less the same as a workstation you are familiar with. The difference is that these nodes are interconnected with special interconnect devices and the way you run your program is slightly different. Across SHARCNET clusters, you are not expected to run your program interactively. You will have to run your program through a queueing system. That also means where and when your program gets to run is not decided by you, but by the queueing system.

What programming languages are supported?

Those primary programming languages such as C, C++ and Fortran are supported. Other languages, such as Java, Pascal and Ada, are also supported, but with limited technical support from us. If your program is written in any language other than C, C++ and Fortran, and you encounter a problem, we may or may not be able solve it within a short period of time. Note: this does not mean you can't use other languages like Matlab, R, Python, Perl, etc. We normally think of those as "scripting" languages, but that doesn't imply that good HPC necessarily requires an explicitly-compiled language like Fortran.

How do I organize my files?

Main file systems on our National systems:


How are file permissions handled at SHARCNET?

By default, anyone in your group can read and access your files. You can provide access to any other users by following this Knowledge Base entry.

All SHARCNET users are associated with a primary GID (group id) belonging to the PI of the group (you can see this by running id username , with your username). This allows for groups to share files without any further action, as the default file permissions for all SHARCNET storage locations (Eg. /gwork/user ) allows read (list) and execute (enter / access) permissions for the group, eg. they appear as:

  [cc_user@gra-login2 ~]$ ls -ld scratch/
   drwxrwx---+ 12 cc_user cc_user 4096 Jul 18 08:59 scratch/

Further, by default the umask value for all users is 0002, so any new files or directories will continue to provide access to the group.

Should you wish to keep your files private from all other users, you should set the permissions on the base directory to only be accessible to yourself. For example, if you don't want anyone to see files in your home directory, you'd run:

chmod 700 ~/

If you want to ensure that any new files or directories are created with different permissions, you can set your umask value. See the man page for further details by running:

man umask

For further information on UNIX-based file permissions please run:

man chmod

What about really large files or if I get the error 'No space left on device' in ~/project or ~/scratch?

If you need to work with really large files we have tips on optimizing performance with our parallel filesystems here.

How do I transfer files/directories to/from or between cluster?


To transfer files to and from a cluster on a UNIX machine, you may use scp or sftp. For example, if you want to upload file foo.f to cluster graham from your machine myhost, use the following command

myhost$ scp foo.f

assuming that your machine has scp installed. If you want to transfer a file from Windows or Mac, you need have scp or sftp for Windows or Mac installed.

If you transfer file foo.f between SHARCNET clusters, say from your home directory on orca to your scratch directory on graham, simply use the following command

[username@orc-login2:~]$ scp foo.f graham:/home/username/

If you are transferring files between a UNIX machine and a cluster, you may use scp command with -r option. For instance, if you want to download the subdirectory foo in the directory project in your home directory on graham to your local UNIX machine, on your local machine, use command

myhost$ scp -rp .

Similarly, you can transfer the subdirectory between SHARCNET clusters. The following command

[username@orc-login2:~]$ scp -rp graham:/home/username/scratch/foo .

will download subdirectory foo from your scratch directory on graham to your home directory on orca (note that the prompt indicates you are currently logged on to orca).

The use of -p option above will preserve the time stamp of each file. For Windows and Mac, you need to check the documentation of scp for features.

You may also tar and compress the entire directory and then use scp to save bandwidth. In the above example, first you login to graham, then do the following

[username@gra-login2:~]$ cd project
[username@gra-login2:~]$ tar -cvf foo.tar foo
[username@gra-login2:~]$ gzip foo.tar

Then on your local machine myhost, use scp to copy the tar file

myhost$ scp .

Note for most Linux distributions, tar has an option -z that will compress the .tar file using gzip.


You may read the instruction using ssh client. [[1]]

How can I best transfer large quantities of data to/from SHARCNET and what transfer rate should I expect?

In general, most users should be fine using scp or rsync to transfer data to and from SHARCNET systems. If you need to transfer a lot of files rsync is recommended to ensure that you do not need to restart the transfer from scratch should there be a connection failure. Although you can use scp and rsync to any cluster's login node(s), it is often best to use - it is dedicated to data transfer.

In general one should expect the following transfer rates with scp:

  • If you are connecting to SHARCNET through a Research/Education network site (ORION, CANARIE, Internet2) and are on a fast local network (this is the case for most users connecting from academic institutions) then you should be able to attain sustained transfer speeds in excess of 10MB/s. If your path is all gigabit or better, you should be able to reach rates above 50 MB/s.
  • If you are transferring data over the wider internet, you will not be able to attain these speeds, as all traffic that does not enter/exit SHARCNET via the R&E net is restricted to a limited-bandwidth commercial feed. In this case one will typically see rates on the order of 1MB/s or less.

Keep in mind that filesystems and networks are shared resources and suffer from contention; if they are busy the above rates may not be attainable

For transferring large amounts of data (many gigabytes) the best approach is to use the online tool Globus.

How do I access the same file from different subdirectories on the same cluster ?

You should not need copy large files on the same cluster (e.g. from one user to another or using the same file in different subdirectories). Instead of using scp you might consider issuing a "soft link" command. Assume that you need access to the file large_file1 in subdirectory /home/user1/subdir1 and you need it to be in your subdirectory /home/my_account/my_dir from where you will invoke it under the name my_large_file1. Then go to that directory and type:

ln -s /home/user1/subdir1/large_file1    my_large_file1

Another example, assume that in subdirectory /home/my_account/PROJ1 you have several subdirectories called CASE1, CASE2, ... In each subdirectory CASEn you have a slightly different code but all of them process the same data file called test_data. Rather than copying the test_data file into each CASEn subdirectory, place test_data above i.e. in /home/my_account/PROJ1 and then in each CASEn subdirectory issue following "soft link" command:

ln -s ../test_data  test_data

The "soft links" can be removed by using the rm command. For example, to remove the soft link from /home/my_account/PROJ1/CASE2 type following command from this subdirectory:

rm -rf test_data

Typing above command from subdirectory /home/my_account/PROJ1 would remove the actual file and then none of the CASEn subdirectories would have access to it.

How are files deleted from the /home/userid/scratch filesystems?

All files on /home/userid/scratch that are over 2 months old (not old in the common sense, please see below) are automatically deleted. Data needed for long term storage and reference should be kept in either ~/project or other archival storage areas. The scratch filesystem is checked at the end of the month for files which will be candidates for expiry on the 15th of the following month. On the first day of the month, a login message is posted and a notification e-mail is sent to all users who have at least one file which is a candidate for purging and containing the location of a file which lists all the candidates for purging.

An unconventional aspect of this system is that it does not determine the age of a file based on the file's attributes, e.g., the dates reported by the stat, find, ls, etc. commands. The age of a file is determined based on whether or not its data contents (i.e., the information stored in the file) have changed, and this age is stored externally to the file. Once a file is created , reading it, renaming, changing the file's timestamps with the touch command, or copying it into another file are all irrelevant in terms of changing its age with respect to the purging system. The file will be expired 2 months after it was created. Only files where the contents have changed will have their age counter "reset".

Unfortunately, there currently exists no method to obtain a listing of the files that are scheduled for deletion. This is something that is being addressed, however there is no estimated time for implementation.

How do I check the age of a file

We define a file's age as the most recent of:

*the access time (atime) and
*the change time (ctime)

You can find the ctime of a file using

[name@server ~]$ ls -lc <filename>

while the atime can be obtained with the command

[name@server ~]$ ls -lu <filename>

We do not use the modify time (mtime) of the file because it can be modified by the user or by other programs to display incorrect information.

Ordinarily, simple use of the atime property would be sufficient, as it is updated by the system in sync with the ctime. However, userspace programs are able to alter atime, potentially to times in the past, which could result in early expiration of a file. The use of ctime as a fallback guards against this undesirable behaviour.

It is also your responsibility to manage the age of your stored data: most of the filesystems are not intended to provide an indefinite archiving service so when a given file or directory is no longer needed, you need to move it to a more appropriate filesystem which may well mean your personal workstation or some other storage system under your control. Moving significant amounts of data between your workstation and a Compute Canada system or between two Compute Canada systems should generally be done using Globus

How to archive my data?

Use tar to archive files and directories

The primary archiving utility on all Linux and Unix-like systems is the tar command. It will bundle a bunch of files or directories together and generate a single file, called an archive file or tar-file. By convention an archive file has .tar as the file name extension. When you archive a directory with tar, it will, by default, include all the files and sub-directories contained within it, and sub-sub-directories contained in those, and so on. So the command tar --create --file project1.tar project1 will pack all the content of directory project1 into the file project1.tar. The original directory will remain unchanged, so this may double the amount of disk space occupied!

You can extract files from an archive using the same command with a different option:tar --extract --file project1.tar. If there is no directory with the original name, it will be created. If a directory of that name exists and contains files of the same names as in the archive file, they will be overwritten. Another option can be added to specify the destination directory where to extract the archive's content.

Compress and uncompress tar files

The tar archiving utility can compress an archive file at the same time it creates it. There are a number of compression methods to choose from. We recommend either xz or gzip, which can be used as follows:

[user_name@localhost]$ tar --create --xz --file project1.tar.xz project1
[user_name@localhost]$ tar --extract --xz --file project1.tar.xz
[user_name@localhost]$ tar --create --gzip --file project1.tar.gz project1
[user_name@localhost]$ tar --extract --gzip --file project1.tar.gz

Typically, --xz will produce a smaller compressed file (a "better compression ratio") but takes longer and uses more RAM while working. --gzip does not typically compress as small, but may be used if you encounter difficulties due to insufficient memory or excessive run time during tar --create. A third option, --bzip2, is also available, that typically does not compress as small as xz but takes longer than gzip.

You can also run tar --create first without compression and then use the commands xz or gzip in a separate step, although there is rarely a reason to do so. Similarly, you can run xz -d or gzip -d to decompress an archive file before running tar --extract, but again there is rarely a reason to do so.

The commands gzip or xz can be used to compress any file, not just archive files:

[user_name@localhost]$ gzip bigfile
[user_name@localhost]$ xz bigfile

These commands will produce the files bigfile.gz and bigfile.xz respectively.

Archival Storage

On Graham, files copied to ~/nearline will be subsequently moved to offline (tape-based) storage. See this link for more details.

How can I check the hidden files in directory?

The "." at the beginning of the name means that the file is "hidden". You have to use the -a option with ls to see it. I.e. ls -a .

If you want to display only the hidden files then type:

ls -d .*

Note: there is an alias which is loaded from /etc/bashrc (see your .bashrc file). The alias is defined by alias l.='ls -d .* --color=auto' and if you type:


you will also display only the hidden files.

How can I count the number of files in a directory?

One can use the following command to count the number of files in a directory (in this example, your /work directory):

find /home/$USER -type f   | wc -l

It is always a good idea to archive and/or compress files that are no longer needed on the filesystem (see below). This helps minimize one's footprint on the filesystem and as such the impact they have on other users of the shared resource.

How to organize a large number of files?

With parallel cluster filesystems, you will get best I/O performance writing data to a small number of large files. Since all metadata operations on each of our parallel filesystems are handled by a single file server, depending on how many files are being accessed the server can become overwhelmed leading to poor overall I/O performance for all users. If your workflow involves storing data in a large number of files, it is best to pack these files into a small number of larger archives, e.g. using tar command

tar cvf archiveFile.tar directoryToArchive

For better performance with many files inside your archive, we recommend to use DAR (Disk ARchive utility), which is a disk analog of tar (Tape ARchive). Dar can extract files from anywhere in the archive much faster than tar. The dar command is available by default on sharcnet systems. It can be used to pack files into a dar archive by doing something like:

dar -s 1G -w -c archiveFile -g directoryToArchive

In this example we split the archive into 1GB chunks, and the archive files will be named archiveFile.1.dar, archiveFile.2.dar, and so on. To list the contents of the archive, you can type:

dar -l archiveFile

To temporarily extract files for post-processing into current directory, you would type:

dar -R . -O -x archiveFile -v -g pathToYourFile/fileToExtract

I am unable to connect to one of the clusters; when I try, I am told the connection was closed by the remote host

The most likely cause of this behaviour is repeated failed login attempts. Part of our security policies involves blocking the IP address of machines that attempt multiple logins with incorrect passwords over a short period of time---many brute-force attacks on systems do exactly this: looking for poor passwords, badly configured accounts, etc. Unfortunately, it isn't uncommon for a user to forget their password and make repeated login attempts with incorrect passwords and end up with that machine blacklisted and unable to connect at all.

A temporary solution is simply to attempt to login from another machine. If you have access to another machine at your site, you can shell to that machine first, and then shell to the SHARCNET system (as that machine's IP shouldn't be blacklisted). In order to have your machine unblocked, you will have to email to as a system administrator must manually intervene in order to fix it.

NOTE: there are other situations that can produce this message, however they are rarer and more transient. If you are unable to log in from one machine, but can from another, it is most likely the IP blacklisting that is the problem and the above will provide a temporary work-around while your problem ticket is processed.

I am unable to ssh/scp from SHARCNET to my local computer

Most campus networks are behind some sort of firewall. If you can ssh out to SHARCNET, but cannot establish a connection in the other direction, then you are probably behind a firewall and should speak with your local system administrator or campus IT department to determine if there are any exceptions or workarounds in place.


Please first read the following:

Suppose you attempt to login to SHARCNET, but instead get an alarming message like this:

Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that the RSA host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
Please contact your system administrator.
Add correct host key in /home/user/.ssh/known_hosts to get rid of this message.
Offending key in /home/user/.ssh/known_hosts:42
RSA host key for requin has changed and you have requested strict checking.
Host key verification failed. 

SSH begins a connection by verifying that the host you're connecting to is authentic. It does this by caching the hosts's "hostkey" in your ~/.ssh/known_hosts file. At times, a hostkey may be changed legitimately; when this happens, you may see such a message. It's a good idea to verify this with us, you may be able to check the fingerprint yourself by logging into another sharcnet system and running:

ssh-keygen -l -f /etc/ssh/ 

If the fingerprint is OK, the normal way to fix the problem is to simply remove the old hostkey from your known_hosts file. On machines with commandline SSH, you can do this with:

ssh-keygen -R thehostname

You can use your choice of editor if you're comfortable doing so (it's a plain text file, but has long lines). On a unix-compatible machine, you can also use the following very small script (Substitute the line(s) printed in the warning message illustrated above for '42' here.):

perl -pi -e 'undef $_ if (++$line == 42)' ~/.ssh/known_hosts

Another solution is brute-force: remove the whole known_hosts file. This throws away any authentication checking, and afterwards, your first connection to any machine will prompt you to accept a newly discovered host key.

Ssh works, but scp doesn't!

If you can ssh to a cluster successfully, but cannot scp to to it, the problem is likely that your login scripts print unexpected messages which confuse scp. scp is based on the same ssh protocol, but assumes that the connection is "clean": that is, that it does not produce any un-asked-for content. If you have something like:

echo "Hello, Master; I await your command..."

scp will be confused by the salutation. To avoid this, simply ensure that the message is only printed on an interactive login:

if [ -t 0 ]; then
    echo "Hello, Master; I await your command..."

or in csh/tcsh syntax:

if ( -t 0 ) then
    echo "Hello, Master; I await your command..."

How do I edit my program on a cluster?

We provide a variety of editors, such as the traditional text-mode emacs and vi (vim), as well as a simpler one called nano. If you have X on your desktop (and tunneled through SSH), you can use the GUI versions (xemacs, gvim).

If your desktop supports FUSE, it's very convenient to simply mount your home tree like this:

mkdir sharcnet
sshfs sharcnet

you can then use any local editor of your choice.

If you run emacs on your desktop, you can also edit a remote file from within your local emacs client using Tramp, opening and saving a file as /

Compiling and Running Programs

For information about compiling your programs on orca, graham and other national Compute Canada systems, please see the Installing software in your home directory page on Compute Canada wiki.

For information about how to compile on older SHARCNET systems, see Legacy Systems.

How do I run a program interactively?

For running interactive jobs on graham and other national systems, see Running jobs page on Compute Canada wiki.

If trying interactive jobs on legacy systems, see Legacy Systems.

My application runs on Windows, can I run it on SHARCNET?

It depends. If your application is written in a high level language such as C, C++ and Fortran and is system independent (meaning it does not depend on any particular third party libraries that are available only for Windows), then you should be able to recompile and run your application on SHARCNET systems. However, if your application completely depends upon a special software for Windows, it will not run on the Linux compute nodes. In general it is impossible to convert code at binary level between Windows and any of UNIX platforms. For options relating to running Windows in virtual machines there is a Creating a Windows VM page at the Compute Canada Wiki.

My application runs on Windows HPC clusters, can I run it on SHARCNET clusters?

If your application does not use any Windows specific APIs then it should be able to recompile and run on SHARCNET UNIX/Linux based clusters.

My program needs to run for more than seven (7) days; what can I do?

The seven day run-time limit on legacy systems cannot be exceeded. This is done to primarily encourage the practice of checkpointing, but it also prevents users from monopolizing large amounts of resources outside of dedicated allocations with long running jobs, ensures that jobs free up nodes often enough for the scheduler to start large jobs in a modest amount of time, and allows us to drain all systems for maintenance within a reasonable time-frame.

In order to run a program that requires more than this amount of wall-clock time, you will have to make use of a checkpoint/restart mechanism so that the program can periodically save its state and be resubmitted to the queues, picking up from where it left off. It is crucial to store checkpoints so that one can avoid lengthy delays in obtaining results in the event of a failure. Investing time in testing and ensuring that one's checkpoint/resume works properly is inconvenient but ensures that valuable time and electricity are not wasted unduly in the long run. Redoing a long calculation is expensive.

Although it is encourage to always use checkpointing for log running work loads, there are a small number of nodes available for 28 day run times on the national general purpose systems Graham and Cedar.

Handling long jobs with chained job submission

On systems that use the Slurm scheduler (e.g. Orca and Graham) job dependencies can be implemented such that the start of one job can be contingent on the completion of another job. This job contingency is expressed via the dependency optional input to sbatch expressed as follows in the job submit script:


Other strategies for resubmitting jobs for long running computations on the Slurm scheduled systems are described on the Compute Canada Wiki.

How do I checkpoint/restart my program?

Checkpointing is a valuable strategy that minimizes the loss of valuable compute time should a long running job be unexpectedly killed by a power outage, node failure, or hitting its runtime limit. On the national systems checkpointing can be accomplished manually by creating and loading your own custom checkpoint files or by using the Distributed MultiThreaded CheckPointing (DMTCP) software without having to recompile your program. For further documentation of the checkpointing and DMTCP software see the Checkpoints page at the Compute Canada Wiki site.

If your program is MPI based (or any other type of program requiring a specialized job starter to get it running), it will have to be coded specifically to save state and restart from that state on its own. Please check the documentation that accompanies any software you are using to see what support it has for checkpointing. If the code has been written from scratch, you will need to build checkpointing functionality into it yourself---output all relevant parameters and state such that the program can be subsequently restarted, reading in those saved values and picking up where it left off.

How can I know when my job would start?

The Slurm scheduler can report expected start times for queued jobs as output from the squeue command. For example the follow command returns the current jobs for user 'username' with columns for job id, job name, start time (N/A if there is no estimate), and job state:

$ squeue -u username -o "%.10i%.24j%.12T%.24S%.24R"
    JOBID                    NAME       STATE              START_TIME        NODELIST(REASON)
 12345678             PENDING                     N/A              (Priority)

It is important to note that the estimated start time listed in the START_TIME column (if available) can change substantially over time. This start time estimate is based on the current state of the compute nodes and list of jobs in the queue. Because the state of the compute nodes and list of jobs in the queue are constantly changing the start time estimates for pending jobs can change for several reasons (running jobs end sooner than expected, higher priority jobs enter the queue, etc). For more information regarding the variables that affect wait times in the queue see the job scheduling policy page at the Compute Canada Wiki site.

Is package X preinstalled on system Y, and, if so, how do I run it?

The software packages that are installed and maintained on the national systems are listed at the available software page of the Compute Canada Wiki site. Some packages have specific documentation for running on the national systems. For the packages that have specific Compute Canada instructions follow the link in the 'Documentation' column of the list of globally installed modules table.

For legacy SHARCNET systems the list of preinstalled packages (with running instructions) can be found on the SHARCNET software page.

Command 'top' gives me two different memory size (virt, res). What is the difference between 'virtual' and 'real' memory?

'virt' refers to the total virtual address space of the process, including virtual space that has been allocated but never actually instantiated, including memory which was instantiated but has been swapped out, and memory which may be shared. 'res' is memory which is actually resident - that is, instantiated with real ram pages. resident memory is normally the more meaningful value, since it may be judged relative to the memory available on the node. (recognizing, of course, that the memory on a node must be divided among the resident pages for all the processes, so an individual thread must always strive to keep its working set a little smaller than the node's total memory divided by the number of processors.)

there are two cases where the virtual address space size is significant. one is when the process is thrashing - that is, has a working set size bigger than available memory. such a process will spend a lot of time in 'D' state, since it's waiting for pages to be swapped in or out. a node on which this is happening will have a substantial paging rate expressed in the 'si' column of output from vmstat (the 'so' column is normally less significant, since si/so do not necessarily balance.)

the second condition where virtual size matters is that the kernel does not implement RLIMIT_RSS, but does enforce RLIMIT_AS (virtual size). we intend to enforce a sanity-check RLIMIT_AS, and in some cases do. the goal is to avoid a node becoming unusable or crashing when a job uses too much memory. current settings are very conservative, though - 150% of physical memory.

in this particular case, the huge V size relative to R is almost certainly due to the way Silky implements MPI using shared memory. such memory is counted as part of every process involved, but obviously does not mean that N * 26.2 GB of ram is in use.

in this case, the real memory footprint of the MPI rank is 1.2 GB - if you ran the same code on another cluster which didn't have numalink shared memory, both resident and virtual sizes would be about that much. since most of our clusters have at least 2GB per core, this code could run comfortably on other clusters.

Can I use a script to compile and run programs?

Yes. For instance, suppose you have a number of source files main.f, sub1.f, sub2.f, ..., subN.f, to compile these source code to generate an executable myprog, it's likely that you will type the following command

ifort main.f sub1.f sub2.f ... sub N.f -llapack -o myprog 

Here, the -o option specifies the executable name myprog rather than the default a.out and the option -llapack at the end tells the compiler to link your program against the LAPACK library, if LAPACK routines are called in your program. If you have long list of files, typing the above command every time can be really annoying. You can instead put the command in a file, say, mycomp, then make mycomp executable by typing the following command

chmod +x mycomp

Then you can just type


at the command line to compile your program.

This is a simple way to minimize typing, but it may wind up recompiling code which has not changed. A widely used improvement, especially for larger/many source files, is to use make. make permits recompilation of only those source files which have changed since last compilation, minimizing the time spent waiting for the compiler. On the other hand, compilers will often produce faster code if they're given all the sources at once (as above).

I have a program that runs on my workstation, how can I have it run in parallel?

If the the program was written without parallelism in mind, then there is very little that you can do to run it automatically in parallel. Some compilers are able to translate some serial portion of a program , such as loops, into equivalent parallel code, which allows you to explore the potential architecture found mostly in symmetric multiprocessing (SMP) systems. Also, some libraries are able to use parallelism internally, without any change in the user's program. For this to work, your program needs to spend most of its time in the library, of course - the parallel library doesn't speed up your program itself. Examples of this include threaded linear algebra and FFT libraries.

However, to gain the true parallelism and scalability, you will need to either rewrite the code using the message passing interface (MPI) library or annotate your program using OpenMP directives. We will be happy to help you parallelize your code if you wish. (Note that OpenMP is inherently limited by the size of a single node or SMP machine - most SHARCNET resources

Also, the preceding answer pertains only to the idea of running a single program faster using parallelism. Often, you might want to run many different configurations of your program, differing only in a set of input parameters. This is common when doing Monte Carlo simulation, for instance. It's usually best to start out doing this as a series of independent serial jobs. It is possible to implement this kind of loosely-coupled parallelism using MPI, but often less efficient and more difficult.

Where can I find available resources?

The information about available computational resources are available to the public as follows:

Can I find my job submission history?

Yes, for SHARCNET maintained legacy systems, you may review the history by logging in to your web account.

For national Compute Canada systems and systems running Slurm, you can see your job submission history from a specific date YYYY-MM-DD by running the following command:

 sacct --starttime YYYY-MM-DD --format=User,JobID%15,Jobname%25,partition%25,state,time,start,end,elapsed,MaxRss,MaxVMSize,nnodes,ncpus,nodelist

where YYYY-MM-DD is replaced with the appropriate date.

How many jobs can I submit in one cluster?

Currently Graham has a limit of 1000 submitted jobs per user.

How are jobs scheduled?

Job scheduling is the mechanism which selects waiting jobs ("queued") to be started ("dispatched") on nodes in the cluster. On all of the major SHARCNET production clusters, resources are "exclusively" scheduled so that a job will have complete access to the CPUs, GPUs or memory that it is currently running on (it may be pre-empted during the course of it's execution, as noted below). Details as to how jobs are scheduled follow below.

How long will it take for my queued job to start?

On national Compute Canada systems and systems running with Slurm, you can see the estimated time your queued jobs will start by running:

 squeue --start -u USER

and replace USER with the name of the account that submitted the job.

What determines my job priority relative to other groups?

The priority of different jobs on the systems is ranked according to the usage by the entire group. This system is called Fairshare. More detail is available here.

Why did my job get suspended?

Sometimes your job may appear to be in a running state, yet nothing is happening and it isn't producing the expected output. In this case the job has probably been suspended to allow another job to run in it's place briefly.

Jobs are sometimes preempted (put into a suspended state) if another higher-priority job must be started. Normally, preemption happens only for "test" jobs, which are fairly short (always less than 1 hour). After being preempted, a job will be automatically resumed (and the intervening period is not counted as usage.)

On contributed systems, the PI who contributed equipment and their group have high-priority access and their jobs will preempt non-contributor jobs if there are no free processors.

My job cannot allocate memory

If you did not specify the amount of memory your job needs when you submitted the job, resubmit the job specifying the amount of memory it needs.

If you specifyed the amount of memory your job needed when it was submitted, then the memory requested was completely consumed. Resubmit your job with a larger memory request. (If this exceeds the available memory desired, then you will have to make your job use less memory.)

Some specific scheduling idiosyncrasies:

One problem with cluster scheduling is that for a typical mix of job types (serial, threaded, various-sized MPI), the scheduler will rarely accumulate enough free CPUs at once to start any larger job. When an job completes, it frees N cpus. If there's an N-cpu job queued (and of appropriate priority), it'll be run. Frequently, jobs smaller than N will start instead. This may still give 100% utilization, but each of those jobs will complete, probably at different times, effectively fragmenting the N into several smaller sets. Only a period of idleness (lack of queued smaller jobs) will allow enough cpus to collect to let larger jobs run.

Note that clusters enforce runtime limits - if the job is still running at the end of the stated limit, it will be terminated. Note also that when a job is suspended (preempted), this runtime clock stops: suspended time doesn't count, so it really is a limit on "time spent running", not elapsed/wallclock time.

How do I run the same command on multiple clusters simultaneously?

If you're using bash and can login with the SSH authentication agent connection forwarding enabled (the -A flag; ie. you've set up ssh keys; see Choosing_A_Password#Use_SSH_Keys_Instead.21 for a starting point) add the following environment variable and function to your ~/.bashrc shell configuration file:

~/.bashrc configuration: multiple cluster command
export SYSTEMS_I_NEED=""
function clusterExec {
  for clus in $SYSTEMS_I_NEED; do
     ping -q -w 1 $clus &> /dev/null
     if [ $? = "0" ]; then echo ">>> "$clus":"; echo ""; ssh $clus ". ~/.bashrc; $1"; else echo ">>> "$clus down; echo ""; fi

You can select the relevant systems in the SYSTEMS_I_NEED environment variable.

To use this function, reset your shell environment (ie. log out and back in again), then run:

clusterExec uptime

You will see the uptime on the cluster login nodes, otherwise the cluster will appear down.

If you have old host keys (not sure why these should change...) then you'll have to clean out your ~/.ssh/known_hosts file and repopulate it with the new keys. If you suspect a problem contact an administrator for key validation or email For more information see Knowledge_Base#SSH_tells_me_SOMEONE_IS_DOING_SOMETHING_NASTY.21.3F.

How do I load different modules on different clusters?

SHARCNET maintained systems provide the environment variables named:

  • $CLUSTER, which is the system's hostname (without or, and
  • $CLU which will resolve to a three-character identifier that is unique for each system (typically the first three letters of the clusters name).

You can use these in your ~/.bashrc to load certain software on a particular system, but not others. For example, you can create a case statement in your ~/.bashrc shell configuration file based on the value of $CLUSTER:

~/.bashrc configuration: loading different modules on different systems
case $CLU in
    # load 2014.6 Intel compiler...
    module unload intel
    module load intel/2014.6
    # load 2018.3 Intel compiler...
    module load intel/2018.3
    # This runs if nothing else matched.

Programming and Debugging

What is MPI?

MPI stands for Message Passing Interface, a standard for writing portable parallel programs which is well-accepted in the scientific computing community. MPI is implemented as a library of subroutines which is layered on top of a network interface. The MPI standard has provided both C/C++ and Fortran interfaces so all of these languages can use MPI. There are several MPI implementations, including OpenMPI and MPICH. Specific high-performance interconnect vendors also provide their own libraries - usually a version of MPICH layered on an interconnect-specific hardware library.

For an MPI tutorial refer to the MPI tutorial.

In addition to C/C++ and Fortran versions of MPI, there exist other language bindings as well. If you have any special needs, please contact us.

What is OpenMP?

OpenMP is a standard for programming shared memory systems using threads with compiler directives instrumented in the source code. It provides a higher-level approach to utilizing multiple processors within a single machine while keeping the structure of the source code as close to the conventional form as possible. OpenMP is much easier to use than the alternative (Pthreads) and thus is suitable for adding modest amounts of parallelism to pre-exiting code. Because OpenMP is a set of programs, your code can still be compiled by a serial compiler and should still behave the same.

OpenMP for C/C++ and Fortran are supported by many compilers, including the PathScale and PGI for Opterons, and the Intel compilers for IA32 and IA64 (such as SGI's Altix.). OpenMP support has been provided in the GNU compiler suite since v4.2 (OpenMP 2.5), and starting with v4.4 supports the OpenMP 3.0 standard.

How do I run an OpenMP program with multiple threads?

An OpenMP program uses a single process with multiple threads rather than multiple processes. On multicore (i.e practically all) systems, threads will be scheduled on available processors, thus run concurrently. In order for each thread to run on one processor, one needs to request the same number of CPUs as the number of threads to use. To run an OpenMP program foo that uses four threads, use the following job submission script.

The option --cpus-per-task=4 specifies to reserve 4 CPUs per process.

#SBATCH --account=def-someuser
#SBATCH --time=0-0:5
#SBATCH --cpus-per-task=4

For a basic OpenMP tutorial refer to OpenMP tutorial.

How do I measure the cpu time when running multi-threaded job?

If you submit a job through the scheduler, then timing information will be collected by the scheduler itself and stored for later query.

If you are running an OpenMP program interactively, you can use the time utility to collect information.

In a typical example using 8 threads,

time ./ompHello

Your output will be something like:

real	0m1.633s
user	0m1.132s
sys	0m0.917s

In this example the real and user time are comparable, so the particular example program is not benefitting from multithreading. In general, real time should be less than user time if parallel execution is occurring.

What mathematics libraries are available?

Every system has the basic linear algebra libraries BLAS and LAPACK installed. Normally, these interfaces are contained in vendor-tuned libraries. On Intel-based (Xeon) clusters it's probably best to use the Intel math kernel library (MKL). On Opteron-based clusters, AMD's ACML library is available. However, either library will work reasonably well on both types of systems. If one expects to do a large amount of computation, it is generally advisable to benchmark both libraries so that one selects the one offering best performance for a given problem and system.

One may also find the GNU scientific library (GSL) useful to some point for their particular needs. The GNU scientific library is an optional package, available on any machine.

For a detailed list of libraries on each clusters, please check the documentation on the corresponding SHARCNET satellite web sites

How do I use mathematics libraries such as BLAS and LAPACK routines?

First you need to know which subroutine you want to use. You need to check the references to find what routines meet your needs. Then place calls to those routines you want in your program and compile your program to use the particular libraries that have those routines. For instance, if you want compute the eigenvalues, and optionally the eigenvectors, of an N by N real non symmetric matrix in double precision, you find the LAPACK routine DGEEV will do that. All you need to do is to have a call to DGEEV, with required parameters as specified in the LAPACK document, and compile your program to link against the LAPACK library.

Now to compile the program, you need to link it to a library that contains the LAPACK routines you call in your code. The general recommendation is to use Intel's MKL library, which has a module loaded by default on most Compute Canada/SHARCNET systems. The instructions on how to link your code with these libraries at compile time are provided on the MKL page.

My code is written in C/C++, can I still use those libraries?

Yes. Most of the libraries have C interfaces. If you are not sure about the C interface or you need assistance in using those libraries written in Fortran, we can help you out on a case to case basis.

What packages are available?

Various packages have been installed on Compute Canada/SHARCNET clusters at users' requests. The full, up to date list is available on the Compute Canada documentation wiki (link). If you do not see a package that you need on this list, please request it by submitting a problem ticket.

You can also search this wiki or the Compute Canada wiki for the package you are interested in to see if there is any additional information about it available.

We can also help you with compiling/installing a package into your own file space if you prefer that approach.

What interconnects are used on SHARCNET clusters?

Currently, several different interconnects are being used on SHARCNET clusters: Quadrics, Myrinet, InfiniBand and standard IP-based ethernet.

Debugging serial and parallel programs

Debugger is a program which helps to identify mistakes ("bugs") in programs - either run-time, or "post-mortem" (by analyzing the core file produced by a crashed program). Debuggers can be either command-line, or GUI (graphical user interface) based. Before a program can be debugged, it needs to be (re-)compiled with a switch, -g, which tells the compiler to include symbolic information into the executable. For MPI problems on the HP XC clusters, -ldmpi includes the HP MPI diagnostic library, which is very helpful for discovering incorrect use of the API.

SHARCNET highly recommends using our commercial debugger DDT. It has a very friendly GUI, and can also be used for debugging serial, threaded, MPI, and CUDA (GPGPU) programs. A short description of DDT and cluster availability information can be found on its software page. Please also refer to our detailed Parallel Debugging with DDT tutorial.

SHARCNET also provides gdb (installed on all clusters, type "man gdb" to get a list of options).

What is NaN ?

NaN stands for "Not a Number". It is an undefined or unrepresentable value, typically encountered in floating point arithmitic (eg. the square root of a negative number). To debug this in your program one typically has to unmask or trap floating point exceptions. This is fairly straightforward with Fortran compilers (e.g. with the Intel's ifort one simply needs to add one switch, "-fpe0"), but somewhat more complicated with C/C++ codes, where the best solution is to use feenableexcept() function.

My program exited with an error code XXX - what does it mean?

Your application crashed, producing an error code XXX (where XXX is a number). What does it mean? The answer may depend on your application. Normally, user codes are not touching the first 130 or so error codes, which are reserved for the Operational System level error codes. On most of our clusters, typing

 perror  XXX

will print a short description of the error. (This is a MySQL utility, and for XXX>122 it will start printing only MySQL-related error messages.) The accurate for the current OS (operational system) list of system error codes can be found on our clusters by printing the content of the file /usr/include/asm-x86_64/errno.h (/usr/include/asm-generic/errno.h on some systems).

Getting Help

I have encountered a problem while using a Compute Canada/SHARCNET system and need help, who should I talk to?

If you have access to the Internet, we encourage you to use the problem ticketing system (described in detail below) . This is the most efficient way of reporting a problem.

You are also welcome to contact system administrators and/or high performance technical computing consultants at any time. You may find their contact information on the directory page.

How long should I expect to wait for support?

Unfortunately Compute Canada/SHARCNET does not have adequate funding to provide support 24 hours a day, 7 days a week. User support and system monitoring is limited to regular business hours: there is no official support on weekends or holidays, or outside 9:00 - 17:00 EST .

Please note that this includes monitoring of our systems and operations, so typically when there are problems overnight or on weekends/holidays system notices will not be posted until the next business day.

Compute Canada Problem Ticket System

What is a "problem ticket system"?

This is a system that allows anyone with a Compute Canada account to start a persistent email thread that is referred to as a "problem ticket". When a user submits a new ticket it will be brought to the attention of an appropriate and available Compute Canada/SHARCNET staff member for resolution.

You can interact with the ticket system entirely via email. There is also a web interface to see tickets you have submitted in the past.

What do I need to specify in a ticket ?

To help us address your question faster, please try to do the following when submitting a ticket:

  1. specify which of our systems is involved
  2. if the problem pertains to a job, then report the jobid associated with the job; this is an integer that is returned by the scheduler when you submit the job
  3. report the exact commands necessary to duplicate the problem, as well as any error output that helps identify the problem; if relevant, this should include how the code is compiled, how the job is submitted, and/or anything else you are doing from the command line relating to the problem
  4. if you'd like for a particular staff member to be aware of the ticket, mention them

How do I submit a ticket?

In general, you can submit a new ticket by emailing with the email address associated with your Compute Canada account. If you are using another email address, please provide your full name, your Compute Canada default username (if available) and your university or institution.

If you like, you can also target your inquiry more specifically, by using the following addresses to submit your ticket:

I am new to parallel programming, can you help me get started with my project?

Absolutely. We will be glad to help you from planning the project, architecting your application programs with appropriate algorithms and choosing efficient tools to solve associated numerical problems to debugging and analyzing your code. We will do our best to help you speed up research. If your programming project would involve a significant staff time, you should consider applying for Dedicated Programming support. (We run the competition annually; see

Can you install a package on a cluster for me?

Certainly. We suggest you make the request by sending e-mail to with the specific request.

I am in a process of purchasing computer equipment for my research, would you be able to provide technical advice on that?

If you tell us what you want, we may be able to help you out.

Does SHARCNET provide any training on programming and using the systems?

Yes. SHARCNET provides workshops on specific topics from time to time and offers courses at some sites. Every summer (usually late May to early June), SHARCNET holds an annual HPC Summer School with a variety of in-depth, hands-on workshops.

SHARCNET also offers a series of online seminars (so-called "General interest webinars"), typically delivered every second Wednesday at lunch time. These are announced via the SHARCNET events mailing list and one can see the schedule at the SHARCNET event calendar. Past seminars are recorded and posted on our youtube channel. A full listing of the past webinars is available on the Online Seminars page.

Attending SHARCNET Webinars

SHARCNET makes a number of seminar events available online (New User Webinar, general interest talks, etc.) using Zoom. Zoom can be used by either installing an app (available for Windows, Mac, Linux etc), or running it in a browser (no installation required). A (free) Zoom account is required for attending our webinars. The Zoom link is provided on the event page in our Events calendar, .

Please note that if your device has a microphone (highly recommended) and/or webcam, they will be used by Zoom to transmit your audio and video to all seminar participants. They are normally off by default, but you can enable them by clicking on a corresponding button at the bottom of your Zoom window - but only when allowed by the host. Normally we do not allow attendees to use their mikes during the webinar, but we have special time for questions and answers at the end of each webinar when the mikes can be enabled. Generally, please keep your mike muted (and webcam disabled) unless you want to ask a question.

We normally record our seminars, and make them available to all SHARCNET users. The recordings are posted on our youtube channel: 

The links to the video recordings, slides and abstracts can be found on our online seminars page.

To subscribe to our events mailing list (which advertises upcoming webinars, summer schools and such), send an email to

To unsubscribe, send an email to

Research at SHARCNET

Where can I find what other people do at SHARCNET?

You may find some of the research activities at SHARCNET by visiting our research initiatives and researcher profile pages.

I have a research project I would like to collaborate on with SHARCNET, who should I talk to?

You may contact SHARCNET head office or contact members of the SHARCNET technical staff.

How can I contribute compute resources to SHARCNET so that other researchers can share it?

Most people's research is "bursty" - there are usually sparse periods of time when some computation is urgently needed, and other periods when there is less demand. One problem with this is that if you purchase the equipment you need to meet your "burst" needs, it'll probably sit, underutilized, during other times.

An alternative is to donate control of this equipment to SHARCNET, and let us arrange for other users to use it when you are not. We prefer to be involved in the selection and configuration of such equipment. Some of SHARCNET's most useful clusters were created this way — Goblin, Wobbie and others were purchased with user contributions, and Orca's newest/fastest nodes are contributed. Our promise to contributors is that as much as possible, they should obtain as much benefit from the cluster as if it were not shared. Owners get preferential access. Naturally, owners are also able to burst to higher peak usage, since their equipment has been pooled with other contributions. (Technically, SHARCNET cannot itself own such equipment — it remains owned by the institution in question, and will be returned to the contributor upon request.) If you think this model will also work for you and you would like to contribute your computational resource to help the research community at SHARCNET, you can contact us for such arrangement.

I do not know much about computation, nor is it my research interest. But I am interested in getting my research done faster with the help of the high performance computing technology. In other words, I do not care about the process and mechanism, but only the final results. Can SHARCNET provide this type of help?

We will be happy to bring the technology of high performance computing to you to accelerate your research, if at all possible. If you would like to discuss your plan with us, please feel free to contact our high performance computing specialists. They will be happy to listen to your needs and are ready to provide appropriate suggestions and assistance.

I am a faculty member from non-SHARCNET member institution. Could I apply for an account and sponsor my student's accounts?

As long as you and your students can obtain a Compute Canada account you will be able to obtain SHARCNET accounts. See above for further information on what is required to obtain an account.

I need access to more CPU cores or storage than are available by default, what programs exist to support demanding computation?

SHARCNET participates in the Compute Canada NRAC (National Resource Allocation Competition) and provides a continual competition for groups that require more than the default level of access to our resources. Please see Dedicated Resources for further information.

I heard SHARCNET offers fellowships, where can I get more information?

SHARCNET no longer actively runs a fellowship program. You may find information regarding past fellowships and other dedicated resource opportunities on the Research Fellowships page of the web portal.

I would like to do some research at SHARCNET as a visiting scholar, how should I apply?

In general, you will need to find a hosting department or a person affiliated with one of the SHARCNET institutions. You may also contact us directly for more specific information.

I would like to send my students to SHARCNET to do some work for me. How should I proceed?

See above.

Contacting SHARCNET

How do I contact SHARCNET for research, academic exchanges, and technical issues?

Please contact SHARCNET head office.

How do I contact SHARCNET for business development, education and other issues?

Please contact SHARCNET head office.

How to Acknowledge SHARCNET in Publications

How do I acknowledge SHARCNET in my publications?

We recommend one cite the following:

This work was made possible by the facilities of the Shared Hierarchical 
Academic Research Computing Network ( and Compute/Calcul Canada.

I've seen different spellings of the name, what is the standard spelling of SHARCNET?

We suggest the spelling SHARCNET, all in upper case.

What types of research programs / support are provided to the research community?

Our overall intent is to provide support that can both respond to the range of needs that the user community presents and help to increase the sophistication of the community and enable new and larger-in-scope applications making use of SHARCNET's HPC facilities. The range of support can perhaps best be understood in terms of a pyramid:

Level 1

At the apex of the pyramid, SHARCNET supports a small number of projects with dedicated programmer support. The intent is to enable projects that will have a lasting impact and may lead to a "step change" in the way research is done at SHARCNET. Inter-disciplinary and inter-institutional projects are particularly welcomed. Projects can expect to receive support at the level of 2 to 6 months direct support per year for one to two years. Programming time is allocated through a competitive process. See the guidelines.

Level 2

The middle layers of support are provided through a number of initiatives.

These include:

  • Programming support of more modest duration (several days to one month engagement, usually part time)
  • Training on a variety of topics through workshops, seminars and online training materials
  • Consultation. This may include user-initiated interactions on particular programs, algorithms, techniques, debugging, optimization etc., as well as unsolicited help to ensure effective use of SHARCNET systems
  • Site Leaders play an important role in working with the community to help researchers connect with SHARCNET staff and to obtain appropriate help and support.

Level 3

The base level of the pyramid handles the very large number of small requests that are essential to keeping the user community working effectively with the infrastructure on a day-to-day basis. Several of these can be answered by this FAQ; many of the issues are presented through the ticketing system. The support is largely problem oriented with each problem being time limited.