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Center for High Throughput Computing

Submitting High Memory Jobs on CHTC's HTC System

The examples and information in the below guide are useful ONLY if:
  • you already have an account on a CHTC-administered submit server
  • your jobs will use more than ~120 GB of memory
To best understand the below information, users should already be familiar with:
  1. Using the command-line to: navigate directories, create/edit/copy/move/delete files and directories, and run intended programs (aka "executables").
  2. CHTC's Intro to Running HTCondor Jobs
  3. CHTC's guides for using Gluster to handle large data and software installation.


A high-memory job is one that requires a significantly larger amount of memory (also known as RAM) than a typical high throughput job usually over 200 GB and up to 1-4 TB. In the following guide, we cover resources and recommendations for running high-memory work in CHTC. However, please make sure to email us if you believe you will need to run "high-memory" work for the first time, or are planning the execution of new "high-memory" work that is different from what you've run before. We'll happily help you with some personalized tips and considerations for getting your work done most efficiently.

  1. High Memory Resources in CHTC
  2. Getting Started
  3. Running High Memory Jobs

1. High Memory Resources in CHTC

Our high memory machines have the following specs:

Machine name Amount of memory Number of CPUs Local disk space on machine
mem1.chtc.wisc.edu 1 TB 80 1 TB
mem2.chtc.wisc.edu 2 TB 80 1 TB
mem3.chtc.wisc.edu 4 TB 80 6 TB
wid-003.chtc.wisc.edu 512 GB 16 2.5 TB

2. Getting Started

A. Identifying High Memory Jobs

Jobs that request over 200GB of memory in their submit file can run on our dedicated high memory machines. However, if your job doesn't need quite that much memory, it's good to request less, as doing so will allow your job(s) to run on more servers, since CHTC has hundreds of servers with up to 100 GB of memory and dozens of servers with up to 250 GB of memory.

B. Testing

Before running a full-size high-memory job, make sure to use a small subset of data in a test job. Not only will this give you a chance to try out the submit file syntax and make sure your job runs, but it can help you estimate how much memory and/or disk you will need for a job using your full data.

You can also use interactive jobs to test commands that will end up in your "executable" script. To run an interactive job, prepare your submit file as usual. Note that for an interactive job, you should use a smaller memory request (and possibly lower CPU and disk as well) than for the final job (so that the interactive job starts) and plan to simply test commands, not run the entire program. To submit interactive job, use the -i flag with condor_submit:

[alice@submit]$ condor_submit -i submit.file
After waiting for the interactive job to start, this should open a bash session on an execute machine, which will allow you to test your commands interactively. Once your testing is done, make the appropriate changes to your executable, adjust your resource requests, and submit the job normally.

C. Consult with Facilitators

If you are unsure how to run high-memory jobs on CHTC, or if you're not sure if everything in this guide applies to you, get in touch with a research computing facilitator by emailing chtc@cs.wisc.edu.

3. Running High Memory Jobs

A. Submit File

The submit file shown in our Hello World example is a good starting point for building your high memory job submit file. The following are places where it's important to customize:

  • request_memory: It is crucial to make this request as accurate as you can by testing at a small scale if possible (see above). Online documentation/help pages or your colleagues' experience is another source of information about required memory.
  • request_cpus: Sometimes, programs that use a large amount of memory can also take advantage of multiple CPUs. If this is the case for your program, you can request multiple CPUs. However, it is always easier to start jobs that request fewer number of cores, rather than more. We recommend:

    Requesting ___ of memory? Request fewer than ___ CPUs
    up to 100 GB 4
    100-500 GB 8
    500GB-1TB 16
    1-1.5TB 20
    1.5-2TB 20
    2TB or greater 32
    If you think a higher CPU request would significantly improve your job's performance, contact a facilitator.
  • request_disk: Request the maximum amount of data your job will ever have within the job working directory on the execute node, including all output and input (which will take up space before some of it is removed from the job working directory at the end of the job).
  • If your software requires newer Linux request our newer operating system (CentOS7):
    requirements = (OpSysMajorVer == 7)
  • Other requirements: if your job uses files from Gluster, or Docker for software, add the necessary requirements for these resources to your submit file.

Altogether, a sample submit file may look something like this:

### Example submit file for a single Gluster-dependent job

universe = vanilla

# Files for the below lines will all be somewhere within /home/username,
# and not within /mnt/gluster/username
log = run_myprogram.log
executable = run_Trinity.sh
output = $(Cluster).out
error = $(Cluster).err
transfer_input_files = trinityrnaseq-2.0.1.tar.gz
should_transfer_files = YES

# Require execute servers that have Gluster
Requirements = (Target.HasGluster == true)

# Memory, disk and CPU requests
request_memory = 200GB
request_disk = 100GB
request_cpus = 4

# Submit 1 job
queue 1
### END

B. Software

Like any other job, the best option for high memory work is to create a portable installation of your software. We have guides for scripting languages and using Docker, and can otherwise provide individual support for program installation during office hours or over email.

C. "Executable" script

As described in many of our guides (for software or for using Gluster), you will need to write a script that will run your software commands for you and that will serve as the submit file "executable". Things to note are:

  • If using files from Gluster, follow the recommendations in our Gluster guide.
  • If using multiple cores, make sure that you request the same number of "threads" or "processes" in your command as you requested in your submit file.

Altogether, a sample script may look something like this (perhaps called run_Trinity.sh):

# Copy input data from Gluster to the present directory of the job
# and un-tar/un-zip them.  
cp /mnt/gluster/usename/reads.tar.gz ./
tar -xzvf reads.tar.gz
rm reads.tar.gz

# Set up the software installation in the job working directory, and 
# add it to the job's PATH
tar -xzvf trinityrnaseq-2.0.6-installed.tar.gz
rm trinityrnaseq-2.0.6-installed.tar.gz
export PATH=$(pwd)/trinityrnaseq-2.0.6:$PATH

# Run software command, referencing input files in the working directory and 
# redirecting "stdout" to a file.  Backslashes are line continuation.
Trinity --seqType fq --left reads_1.fq \
--right /mnt/gluster/username/path/to/reads_2.fq --CPU 4 --max_memory \
20G > trinity_stdout.txt

# Trinity will write output to the working directory by default, 
# so when the job finishes, it needs to be moved back to gluster
tar -czvf trinity_out_dir.tar.gz trinity_out_dir
cp trinity_out_dir.tar.gz trinity_stdout.txt /mnt/gluster/username/
rm reads_*.fq trinity_out_dir.tar.gz trinity_stdout.txt

### END