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Running mcmicro on the O2 compute cluster

O2 is a high-performance cluster at Harvard Medical School (HMS). Non-HMS users can safely ignore this page.

Familiarity with basic O2 commands will make running MCMICRO much easier on O2. If this is your first time interacting with the platform, please check out HMS’s O2 documentation.

Setting up for MCMICRO on O2

  1. Follow installation instructions to install Nextflow. Docker is not needed, because O2 uses Singularity to execute module containers, and Singularity is already available on O2.

  2. Please ensure that Java is available by running module load java.

  3. If your account is not in the HITS_lsp-analysis group (type groups to check), then please run the following command to prepare your environment: nextflow run labsyspharm/mcmicro/setup/

  4. When working with exemplars, please download your own copy to /n/scratch/users/.../$USER/ (where $USER is your eCommons ID and ... is its first letter).

O2 execution

To run the pipeline on O2, the following additional steps are required:

  1. If your account is in the HITS_lsp-analysis group, please add the flag -profile O2. Use -profile O2,WSI and -profile O2,TMA for very large whole-slide images (WSIs) and tissue microarrays (TMAs), respectively. The profiles differ in the amount of resources requested for each module.
  2. If your account is not in the HITS_lsp-analysis group, please use -profile O2ext. Similarly, use -profile O2ext,WSI and -profile O2ext,TMA for WSIs and TMAs.
  3. To avoid running over on your disk quota, it is also recommended to use /n/scratch for holding the work/ directory. Furthermore, /n/scratch is faster than /home or /n/groups, so jobs will complete faster.

Compose an sbatch script that encapsulates resource requests, module loading and the nextflow command into a single entity. Create a file based on the following template:

#SBATCH -p short
#SBATCH -J mcmicro              
#SBATCH -o mcmicro-%J.log
#SBATCH -t 0-12:00
#SBATCH --mem=1G
#SBATCH --mail-type=END         # Type of email notification- BEGIN,END,FAIL,ALL
#SBATCH   # Email to which notifications will be sent

module purge
module load java
/home/$USER/bin/nextflow run labsyspharm/mcmicro --in /n/scratch/users/${USER:0:1}/$USER/exemplar-001 -profile O2 -w /n/scratch/users/${USER:0:1}/$USER/work

replacing relevant fields (e.g., with your own values.

The pipeline run can then be kicked off with sbatch

Requesting O2 resources

The default profiles WSI and TMA establish reasonable defaults for O2 resource requests. These will work for most scenarios, but individual projects may also have custom time and memory requirements. To overwrite the defaults, compose a new config file (e.g., myproject.config) specifying the desired custom requirements using process selectors. For example, to request 128GB of memory and 96 hours in the medium queue for ASHLAR, one would specify

  withName:ashlar {
    queue  = 'medium'
    time   = '96h'
    memory = '128G'

Use existing profiles as examples. Once myproject.config is composed, it can be provided to a nextflow run command using the -c flag:

nextflow run labsyspharm/mcmicro --in /path/to/exemplar-001 -profile O2 -c myproject.config

Note that -profile is still needed because it defines additional configurations, such as where to find the container modules. myproject.config simply overrides a portion of the fields in the overall profile.