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This is a 30-mins getting started. Check out our complete documentation in HPC and our How To's page for useful examples.

To submit parallel jobs or serial jobs longer than 6 hours, contact us for production resources: dalma.admins@nyu.edu

Prerequisite

Before submitting jobs on Dalma, please make sure that you are familiar with the following basic Linux topics:

  • How to login a remote host using ssh.
  • How to manage (create, remove, move and copy) files and directories.
  • How to edit a file without GUI using simple text editor (vi, nano or emacs).
  • User / Group structure and file permission (e.g., what does "ls: cannot open directory : Permission denied" mean?).
  • Reading and writing files with commands like head, tail, cat, and less
  • I/O redirection (e.g., stdout, stderr, >, 2>, >>)
  • Environmental variables like $PATH and $LD_LIBRARY_PATH (e.g., what does "-bash: matlab: command not found" mean?)

If not, we strongly advise you to learn these topics. This could very likely save you days in the future. There are plenty of tutorials freely available online:

Usage Model

Dalma is accessed through a dedicated set of login nodes, which are designed for light-weight, short period tasks. Access to the compute, GPU and visualization nodes for production runs, is controlled by the workload manager Slurm. The production jobs are submitted on login nodes to Slurm. Then Slurm will schedule and run these jobs on compute nodes.

 

Dalma Access Model

Getting and Renewing an Account

First you need a valid NetID (NYU Home Page). Then, to request or renew your access to NYUAD HPC, please follow the instructions in this page: Accounts, and go to the NYU High Performance Computing (HPC) account management site with your NetID: https://iiq.home.nyu.edu/identityiq

Ask for a sponsor to get access

All NYUAD staff and students must have a faculty sponsor. Click here for more information.

 

Access

Connect to NYU-VPN as instructed here before connecting to Dalma if you are outside NYUNET. Alternatively, connect to bastion host as described here Access Dalma.

Once you have an HPC account, you are ready to access a cluster. In the most simple case:

Login Dalma

If you are using Windows, or prefer GUI to terminal, check this page Access Dalma for instructions.

Storage System

Right after login to Dalma, user is automatically directed to $HOME. Dalma storage consists of 4 filesystems: $HOME (/home/<Net-ID>), $FASTSCRATCH (/fastscratch/<Net-ID>), $SCRATCH (/scratch/<Net-ID>) and $ARCHIVE (/archive/<Net-ID>) that can be referenced through the environment variables $HOME, $FASTSCRATCH, $SCRATCH and $ARCHIVE. Notice that $HOME is for small permanent storage, $FASTSCRATCH is for large infrequent reads and writes, $ARCHIVE is for long-term storage. $SCRATCH is for large infrequent reads and writes with large files. The access to $FASTSCRATCH is upon request and approval.

HOME is limited.

The quota of $HOME is only 5GB. Run myquota in terminal on Dalma to check your current usage.

Access different files systems using environmental variables

Backup your FASTSCRATCH and SCRATCH

Files not accessed for 90 days at $FASTSCRATCH and $SCRATCH will be deleted.

Summary of storage

Submit your job and prepare your input / output in $SCRATCH

Put your source code, applications and executable in $HOME

Back up your data in $ARCHIVE

Contact us for usage in $FASTSCRATCH

Data Transfer

You can use either Terminal or FileZilla to transfer your data from / to Dalma, as instructed here. File Transfer using rsync and File Transfer using FileZilla.

Hardware Overview

Users can not acquire all physical memory on nodes in their job scripts. Some memory is reserved for system. See the form below.

Node TypeNumber of NodesHardware per NodeMaximum Memory Per Node User Can RequireNote
Standard Compute236128GB, 28 cores, Broadwell112GB 
Fat8192GB memory, 12 cores, Westmere180GB 
Super Fat1

1TB memory, 32 cores, Westmere

1000GB 
Ultra Fat12TB memory, 72 cores, Broadwell2000GBConsult with us for access to this node
GPU1696GB memory, 12 cores, Westmere, NVIDIA GPU90GB 
Login4

128GB, 28 cores, Broadwell

  
Visualization (incoming)    

 

 

Software Overview

We now have available a new Module Environment in Dalma, which is part of the User Centric Approach that we have been promoting from NYUAD to manage the software stack. This new Module Environment, NYUAD 3.0 overcome the flaws of the traditional modules environment when used to manage complex modern software environments.

First, you could check what applications are available

Then you could select the desired software to load. The following example shows how to load a self-sufficient-single-application environment for gromacs.

Load a self-sufficient-single-application environment for Gromacs

Thie following example shows how to load an environment for compiling source code from scratch.

Load GCC, OpenMPI and FFTW for Compiling Source Code


Batch System

The batch system on Dalma is the Slurm (Simple Linux Utility for Resource Management), a free open-source resource manager by LLNL. Similar to most supercomputers, on Dalma, production jobs are submitted to the batch system.  In order to submit a job you need to create a submission script where you specify your resources requirements. Before jobs are dispatched to run they are put onto partitions waiting for available processing resources. There are partitions for various types of use. Parallel partition will allocate entire nodes to the job (i.e. only 1 job per node). Serial partition allows multiple jobs to share one node. 

Available Partitions (Queues)

We abstract 3 partitions for users. 

  1. serial: For job using no more than 1 node.
  2. parallel: For job using more than 1 node.
  3. preempt: For serial jobs which could be re-queued and less than 30 minutes walltime.

Job Limit

Please refer to this page to check what job limit applies to you according to your affiliation.

Writing a Batch Script

A job script is a text file describing the job, resources required. Slurm has its unique directives, but is similar in many ways to PBS or LSF. Moreover, Slurm maintaned a good compability on PBS script. In many case, PBS script is directly acceptable. 

To submit parallel jobs or serial jobs longer than 6 hours, contact us for production resources: dalma.admins@nyu.edu

Serial Job Example

  1. A typical Slurm serial job script looks like this. Let say you save it as serial-job.sh

    Typical Serial Job Script in Slurm

    Below, your will find a generic Slurm job scripts will gentle explanation with each directives.

  2. Then you can submit the saved job script serial-job.sh with:

    Submitting a Serial Job

Parallel Job Example

To submit parallel jobs or serial jobs longer than 6 hours, contact us for production resources: dalma.admins@nyu.edu

  1. A typical Slurm parallel job script looks like this. Let say you save it as parallel-job.sh

    Typical Parallel Job Script in Slurm
  2. Then you can submit the saved job script parallel-job.sh with:

    Submitting a Parallel Job

Submitting a Job

Please be aware that submitting jobs is only possible from login nodes at the moment. Contact us if you need help.

Command sbatch is for submitting jobs. A simple example:

Minimal Example of Job Submission

After the submission, it will return the corresponding job id. Once scheduled for run, the script is executed on the first compute node in the allocation.

Checking Job Status

Before and During Job Execution

This command gives you all the jobs by a certain user.

List all current jobs for a user

Example output:

It means the job with Job ID 31408, has been running (ST: R) for 2 minutes on compute-21-4.

For more verbose information, use scontrol show job.
Getting Verbose Information on a Job

After Job Execution

Once the job is finished, the job can't be inspected by squeue or scontrol show job. At this point, you could inspect the job by sacct.

Checking a Job

The following commands give you extremely verbose information on a job.

Getting Verbose Information on a Job

 

Canceling a Job

If you decide to end a job prematurely, use scancel

Use with Cautions

To cancel all jobs from your account. Run this on Dalma terminal.

Interactive Sessions

To start an interactive session, use srun command:


salloc is not allowed

Use srun for interactive mode.


 

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