What is Sherlock?

Sherlock is a high-performance computing (HPC) cluster available for research at Stanford and operated by the Stanford Research Computing Center. Sherlock is a “condo-model” cluster with a public access portion and an owner portion with nodes purchased by active research groups. Anyone at Stanford can use Sherlock for free, on the public nodes. However only owners can use the owner nodes as well. Owners have priority over their own nodes, but can run jobs that get scheduled on nodes not actively being used by their owners.

Sherlock is a batch submission environment like FarmShare and Yen-Slurm, not an interactive computing environment like the yens. That is, you can’t just log in and run intensive tasks. To compute on Sherlock, you have to prepare and submit a slurm job script that describes the CPU, memory (RAM), and time resources you require, as well as the code to run. A scheduler puts your requests in queue until the resources can be allocated. Note that this probably requires you to have an understanding of what resources your job will require ahead of submission.

Sherlock has over 1,600 compute nodes with 44,000+ CPU cores. It is divided into several logical partitions that are either accessble for everyone to use (normal) or you have to buy in to use them. A PI group can purchase its own nodes and have its own partition. Buying nodes gives you access to the large owners partition where you can run jobs on nodes while the PI group who owns them is not using them.

How do I use Sherlock?

Getting Sherlock Account

For a GSB faculty member, we can create a Sherlock account with your own PI group that will give you access to the gsb partition. If you are a PhD student, you will need to have a faculty sponsor you to gain access to Sherlock.

Once you have an account, login to Sherlock.

$ ssh <$USER>

Enter your SUNet ID and Duo authenticate to login.

Sherlock uses Slurm to schedule jobs and manage the queue of pending jobs. We can use the same slurm commands to get information about the cluster and a queue of jobs as well as use similar submission scripts to the ones we used on Yen-Slurm to run jobs on Sherlock.

Get information about the cluster:

$ sinfo

See the queue on a normal partition:

$ squeue -p normal

To get information about partitions that are available to you, run

$ sh_part

GSB Sherlock Partition

DARC currently owns three nodes in the Sherlock cluster and software licenses for Matlab and Stata-MP. Our Stata-MP license is a 64-core license, much larger than the 16-core licenses available on the yens.

Right now, GSB has its own partition, gsb, which the GSB faculty PI groups can access. The gsb partition is comprised of three nodes, one with 20 cores and 125 G of RAM and two larger nodes, each with 128 cores and 1 T of RAM.

Tasks that are probably suitable for Sherlock are:

  • Parameter Sweeps: you need to run the same code many times, but with different inputs
  • Resource Guarantees: you need to know that your code will have a specific amount of CPU or Memory (RAM) for the duration of its run
  • Large Compute: you need more CPU/memory resources than is “fair” to use at a time on the yens
  • Parallelization: you code in C/C++, and can use MPI for code parallelization across nodes
  • Deep learning / machine learning on GPU’s: your code uses a deep learning framework like Keras or PyTorch that can utilize the GPUs for training and prediction

Be advised that Sherlock isn’t a magic bullet for getting a large amount of work done quickly. Submitting work to Sherlock requires careful thought about how your analysis is organized to effectively be submitted and run. DARC can help you evaluate your options and plan for success.


Python Example

The python script is a simple hello world script that prints hello and hostname of the node where it is running then sleeps for 30 seconds.

import socket
import time

# print hostname of the node
print('Hello from {} node').format(socket.gethostname())

Slurm Script

We can use the following slurm script, hello.slurm, that will submit the above python script and use any of the three partitions that I have permission to submit to:


# Example of running python script 

#SBATCH -J hello
#SBATCH -p normal,gsb,dev
#SBATCH -c 1                            # one CPU core 
#SBATCH -t 5:00
#SBATCH -o hello-%j.out
#SBATCH --mail-type=ALL

# Load software
module load python/3.6.1

# Run python script 

Submit with:

$ sbatch hello.slurm

Monitor the queue:

$ watch squeue -u $USER

You might see job’s status as CF (configuring) when the job starts and CG (completing) when the job finishes.

Once the job is finished, look at the output:

$ cat hello-$JOBID.out

You should see a similar output:

Hello from node

Large Job Array Example

Now, we want to run a large job array. First, let’s check user job limits for the normal partition with:

$ sacctmgr show qos normal

to find that MaxTRESPU limit is 512 CPUs max so we will need to limit our job array to 512 CPU cores.

We can modify the hello world python script and call it to also print a job task ID.

import sys
import socket
import time

# print task number and hostname of the node
print('Hello! I am a task number {} on {} node').format(sys.argv[1], socket.gethostname())

We use the following slurm script, hello-job-array.slurm, that will submit 512 job array tasks and use either normal or the gsb partition where I have permission to submit to:


# Example of running python script with a job array

#SBATCH -J hello
#SBATCH -p normal,gsb
#SBATCH --array=1-512                    # how many tasks in the array
#SBATCH -c 1                             # one CPU core per task
#SBATCH -t 5:00
#SBATCH -o out/hello-%A-%a.out
#SBATCH --mail-type=ALL

# Load software
module load python/3.6.1

# Run python script with a command line argument

Submit with:

$ sbatch hello-job-array.slurm

Monitor the queue:

$ watch squeue -u $USER

Deep learning on GPU

Sherlock also has over 700+ GPUs that we can take advantage of when training machine learning / deep learning models.

This is an abbreviated version of this topic guide that also talks about how to setup your conda environment on Sherlock to be able to run the Keras example below.

We will run this python script, on the Sherlock GPU to train a simple MNIST convnet.

import numpy as np
from tensorflow import keras
from tensorflow.keras import layers

# Model / data parameters
num_classes = 10
input_shape = (28, 28, 1)

# the data, split between train and test sets
(x_train, y_train), (x_test, y_test) = keras.datasets.mnist.load_data()

# Scale images to the [0, 1] range
x_train = x_train.astype("float32") / 255
x_test = x_test.astype("float32") / 255
# Make sure images have shape (28, 28, 1)
x_train = np.expand_dims(x_train, -1)
x_test = np.expand_dims(x_test, -1)
print("x_train shape:", x_train.shape)
print(x_train.shape[0], "train samples")
print(x_test.shape[0], "test samples")

# convert class vectors to binary class matrices
y_train = keras.utils.to_categorical(y_train, num_classes)
y_test = keras.utils.to_categorical(y_test, num_classes)

# build the model
model = keras.Sequential(
        layers.Conv2D(32, kernel_size=(3, 3), activation="relu"),
        layers.MaxPooling2D(pool_size=(2, 2)),
        layers.Conv2D(64, kernel_size=(3, 3), activation="relu"),
        layers.MaxPooling2D(pool_size=(2, 2)),
        layers.Dense(num_classes, activation="softmax"),


# train the model
batch_size = 128
epochs = 15

model.compile(loss="categorical_crossentropy", optimizer="adam", metrics=["accuracy"]), y_train, batch_size=batch_size, epochs=epochs, validation_split=0.1)

# evaluate the trained model
score = model.evaluate(x_test, y_test, verbose=0)
print("Test loss:", score[0])
print("Test accuracy:", score[1])

The submission script keras-gpu.slurm looks like:


# Example slurm script to run keras DL models on Sherlock GPU

#SBATCH -J train-gpu
#SBATCH -p gpu
#SBATCH -c 20
#SBATCH -t 2:00:00
#SBATCH -G 1                          # how many GPU's you want
#SBATCH -o train-gpu-%j.out
#SBATCH --mail-type=ALL

# For safety, we deactivate any conda env that might be activated on interactive yens before submission and purge all loaded modules
source deactivate
module purge

# Load software
module load cuda/11.0.3

# Activate the environment
source activate tf-gpu

# Run python script

This script is asking for one GPU (-G 1) on gpu partition and 20 CPU cores on one node for 2 hours.

It also loads necessary CUDA module and activates the conda environment where I previously installed the python packages for this script.

Submit the job to the gpu partition with:

$ sbatch keras-gpu.slurm

Monitor your job:

$ squeue -u $USER

You should see something like:

          20372833       gpu train-gp nrapstin  R       0:05      1 sh03-12n07

Once the job is running, connect to the node where your job is running to monitor GPU utilization:

$ ssh sh03-12n07

Once you connect to the GPU node, load the cuda module there and monitor GPU utilization while the job is running:

$ module load cuda/11.0.3
$ watch nvidia-smi

You should see that the GPU is being utilized (GPU-Util column):

Every 2.0s: nvidia-smi                                                                                         
Tue Nov 15 13:43:04 2022
| NVIDIA-SMI 520.61.05    Driver Version: 520.61.05    CUDA Version: 11.8     |
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|                               |                      |               MIG M. |
|   0  NVIDIA GeForce ...  On   | 00000000:C4:00.0 Off |                  N/A |
|  0%   44C    P2   114W / 260W |  10775MiB / 11264MiB |     40%   E. Process |
|                               |                      |                  N/A |

| Processes:                                                                  |
|  GPU   GI   CI        PID   Type   Process name                  GPU Memory |
|        ID   ID                                                   Usage      |
|    0   N/A  N/A      4876	 C   python                          10772MiB |

Once the job is done, look at the output file:

$ cat train-gpu*.out