TensorFlow

TensorFlow is "an open-source software library for Machine Intelligence".

Installing TensorFlow

These instructions install Tensorflow into your home directory using Compute Canada's pre-built Python wheels. Custom Python wheels are stored in /cvmfs/soft.computecanada.ca/custom/python/wheelhouse/. To install TensorFlow's wheel we will use the pip command and install it into a Python virtual environment. The below instructions install for Python 3.5.2 but you can also install for Python 3.5.Y or 2.7.X by loading a different Python module.

Load modules required by TensorFlow:

[name@server ~]$ module load python/3.5.2

Create a new Python virtual environment:

[name@server ~]$ virtualenv tensorflow

Activate your newly created Python virtual environment:

[name@server ~]$ source tensorflow/bin/activate

Install TensorFlow into your newly created virtual environment using the command from either one of the two following subsections.

CPU-only

(tensorflow) [name@server $] pip install tensorflow-cpu

GPU

(tensorflow) [name@server $] pip install tensorflow-gpu

Submitting a TensorFlow job with a GPU

Once you have the above setup completed you can submit a TensorFlow job as

[name@server ~]$ sbatch tensorflow-test.sh

The job submission script has the content

File : tensorflow-test.sh

#!/bin/bash
#SBATCH --gres=gpu:1        # request GPU "generic resource"
#SBATCH --cpus-per-task=6   # maximum CPU cores per GPU request: 6 on Cedar, 16 on Graham.
#SBATCH --mem=32000M        # memory per node
#SBATCH --time=0-03:00      # time (DD-HH:MM)
#SBATCH --output=%N-%j.out  # %N for node name, %j for jobID

module load cuda cudnn python/3.5.2
source tensorflow/bin/activate
python ./tensorflow-test.py

while the Python script has the form,

File : tensorflow-test.py

import tensorflow as tf
node1 = tf.constant(3.0, dtype=tf.float32)
node2 = tf.constant(4.0) # also tf.float32 implicitly
print(node1, node2)
sess = tf.Session()
print(sess.run([node1, node2]))

Once the above job has completed (should take less than a minute) you should see an output file called something like cdr116-122907.out with contents similar to the following example,

File : cdr116-122907.out

2017-07-10 12:35:19.489458: I tensorflow/core/common_runtime/gpu/gpu_device.cc:940] Found device 0 with properties:
name: Tesla P100-PCIE-12GB
major: 6 minor: 0 memoryClockRate (GHz) 1.3285
pciBusID 0000:82:00.0
Total memory: 11.91GiB
Free memory: 11.63GiB
2017-07-10 12:35:19.491097: I tensorflow/core/common_runtime/gpu/gpu_device.cc:961] DMA: 0
2017-07-10 12:35:19.491156: I tensorflow/core/common_runtime/gpu/gpu_device.cc:971] 0:   Y
2017-07-10 12:35:19.520737: I tensorflow/core/common_runtime/gpu/gpu_device.cc:1030] Creating TensorFlow device (/gpu:0) -> (device: 0, name: Tesla P100-PCIE-12GB, pci bus id: 0000:82:00.0)
Tensor("Const:0", shape=(), dtype=float32) Tensor("Const_1:0", shape=(), dtype=float32)
[3.0, 4.0]

TensorFlow can run on all GPU node types. Cedar's GPU large node type, which is equipped with 4 x P100-PCIE-16GB with GPUDirect P2P enabled between each pair, is highly recommended for large scale Deep Learning or Machine Learning research. See Using GPUs with SLURM for more information.

Benchmarks

This section will give ResNet-50 and VGG-16 benchmarking results on both Graham and Cedar with single and multiple GPUs using different methods for managing variables. The benchmark can be found on github: TensorFlow Benchmarks.

Methods of managing variables:

ps, cpu: --variable_update=parameter_server --local_parameter_device=cpu

ps, gpu: --variable_update=parameter_server --local_parameter_device=gpu

replicated: --variable_update=replicated

replicated, xring: --variable_update=replicated --all_reduce_spec=xring

replicated, pscpu: --variable_update=replicated --all_reduce_spec=pscpu

replicated, nccl: --variable_update=replicated --all_reduce_spec=nccl

Data Format

For GPU which uses cuDNN, NCHW should be used. This is the default one for this benchmarking code.

--data_format=NCHW

For others, NHWC (TF native) is suggested.

--data_format=NHWC

ResNet-50

Batch size is 32 per GPU. Data parallelism is used. Results in "images per second".

Node type	Single GPU baseline	Number of GPUs	ps,cpu	ps, gpu	replicated	replicated, xring	replicated, pscpu	replicated, nccl
Graham GPU node	171.23	2	93.31	324.04	318.33	316.01	109.82	315.99
Cedar GPU Base		4
Cedar GPU Large	205.71	4	673.47	721.98	754.35	574.91	664.72	692.25

VGG-16

Batch size is 32 per GPU. Data parallelism is used. NCCL runs the best for all kinds of node types. (Results in "images per second")

Node type	Single GPU baseline	Number of GPUs	ps,cpu	ps, gpu	replicated	replicated, xring	replicated, pscpu	replicated, nccl
Graham GPU node	115.89	2	91.29	194.46	194.43	203.83	132.19	219.72
Cedar GPU Base	114.77	4	232.85	280.69	274.41	341.29	330.04	388.53
Cedar GPU Large	137.16	4	175.20	379.80	336.72	417.46	225.37	490.52