FlexFlow

A distributed deep learning framework that supports flexible parallelization strategies.

Prerequisties

• CUDNN is used to perform low-level operations.

• Legion is the underlying runtime FlexFlow built on.

• (Optinal) GASNet is used for multi-node executions. (see installation instructions)

After you have cloned FlexFlow, use the following command lines to clone Legion and GASNet.

git submodule init
git submodule update

Compilation

• Download FlexFlow source code:

# Using git to download FlexFlow
git clone --recursive https://gitlab.com/fflow/flexflow

• Build a DNN model (e.g., alexnet):

./ffcompile.sh examples/alexnet

where examples/alexnet.cc defines all operators in a DNN.

• To build a distributed version of FlexFlow, add a -d flag:

./ffcompile.sh -d alexnet

Parallelization Strategy

Flexflow accepts any parallelization strategy in layer-wise parallelism (see ) to parallelize training. A parallelization strategy should describe how to parallelize each operator in a DNN. An example parallelization strategy for AlexNet is as follows.

Layer	Type	Configuration	Devices
conv1	conv2d	n=4 c=1 h=1 w=1	0 1 2 3
pool1	pool2d	n=4 c=1 h=1 w=1	0 1 2 3
conv2	conv2d	n=1 c=1 h=2 w=2	0 2 1 3
pool2	pool2d	n=1 c=1 h=2 w=2	0 2 1 3
flat1	flat	n=2 c=1	0 2
linear1	linear	n=1 c=3	0 2 3
linear2	linear	n=1 c=3	0 1 2
linear3	linear	n=1 c=1	0
Some example parallelization strategies are available in the strategies subfolder.

Training a DNN model

To train a DNN model, run the complied application with the path to the training dataset, the path to the parallelization strategy, and some additional configuration flags. For example:

./alexnet -e 10 -b 256 --lr 0.1 --wd 1e-4 -p 10 -d path_to_dataset -s path_to_strategy -ll:gpu 4 -ll:fsize 90000 -ll:zsize 5000 -ll:cpu 4

• -e or --epochs: number of total epochs to run (default: 90)
• -b or --batch-size: global batch size in each iteration (default: 64)
• --lr or --learning-rate: initial learning rate (default: 0.1)
• --wd or --weight-decay: weight decay (default: 1e-4)
• -p or --print-freq: print frequency (default 10)
• -d or --dataset: path to the training dataset. If not set, synthetic data is used to conduct training.
• -s or --strategy: path to the strategy to parallelize training. If not set, data parallelism is used as the default strategy.
• -ll:gpu: number of GPU processors to use on each node
• -ll:fsize: size of device memory on each GPU (in MB)
• -ll:zsize: size of zero-copy memory (pinned DRAM with direct GPU access) on each node (in MB). This is used for prefecthing training images from disk.
• -ll:cpu: number of data loading workers (default: 4)

Publication

Zhihao Jia, Sina Lin, Charles R. Qi, and Alex Aiken. Exploring Hidden Dimensions in Parallelizing Convolutional Neural Networks. In Proceedings of the International Conference on Machine Learning (ICML), Stockholm, Sweden, July 2018.