Implementation of ACM CIKM 2017 paper Learning Edge Representation via Low-Rank Asymmetric Projections. As described below, this repository includes:

1. Code to process a graph (i.e. create training files).
2. Code to train node embeddings and edge function, using our method, and evaluation code on link prediction tasks.
3. Dataset files, that are used in our paper.

If you use this code, then you should:

1. Note that this is not an official Google product. Please direct your questions to the main author (Sami Abu-El-Haija).

2. Consider citing our work, using the following bibtex:

   @INPROCEEDINGS{asymproj,
     authors = {Sami Abu-El-Haija AND Bryan Perozzi AND Rami Al-Rfou},
     title = {Learning Edge Representations via Low-Rank Asymmetric Projections},
     booktitle = {ACM International Conference on Information and Knowledge Management (CIKM)},
     year = {2017},
   }
   

• create_dataset_arrays.py: Processes a graph, as an edge-list file, and produces training files.
• deep_edge_trainer.py: Processes the output of create_dataset_arrays.py and trains a model, continuously evaluating the model on the test partition.
• datasets/: Directory containing datasets used in our paper. The original datasets come from Stanford SNAP and BioGrid. Nonetheless, we release our train/test splits for others to replicate our results.

To use, you must first create dataset files (using create_dataset_arrays.py), then train the node embeddings and the edge function (using deep_edge_trainer.py). The following two subsections explain how to use these two python scripts.

The input to our method is an edge-list (readable by nx.read_edgelist). In particular, assume that your file /path/to/graph.txt contains lines like:

n1 n2

where n1 and n2 are node IDs, which can be strings or integers. The line indicates edge n1-n2 (if graph is undirected) or n1->n2 (if graph is directed). Assume that the above graph.txt contains |E| lines. You can generate dataset files by running:

python create_dataset_arrays.py --input /path/to/graph.txt --output ~/asymproj/datasets/my_graph

Which creates directory ~/asymproj/datasets/my_graph, writing files:

1. train.txt.npy and test.txt.npy: int32 numpy arrays, each of size (|E|/2, 2), containing train and test edges. They union to graph.txt, except that the node IDs are renumbered to be [0, 1, 2, ..., |V| - 1].
2. train.neg.txt.npy and test.neg.txt.npy: int32 numpy arrays, each of size (|E|/2, 2), containing negative edges for training and testing. The first is sampled from the compliment of train.txt.npy and the second is sampled from the compliment of union(train.txt.npy, test.txt.npy).
3. test.directed.neg.txt.npy only if --directed flag is set. It is set to contents of test.neg.txt.npy plus all (u, v) if (v, u) is an edge but (u, v) is not. These are harder negatives that evaluates the capability of the edge representation to learn edge direction.
4. index.pkl: Pickle serialization of python dictionary containing graph statistics, as well as key 'index' that is a mapping of original node ID -> renumbered node ID.
5. train.neg_per_node.txt.npy: pre-sampled 20 negative nodes per node, used for noise estimation.
6. train.pairs.<i>.txt.npy: Training pairs. Sampled using random walks. Presence of pair (u, v), indicates that u and v appeared in a random walk, within --context hops.

If you are using pre-processed dataset files, with {train, test} and {positive, negative} edges generated as numpy files, you can simulate walks on train positives and create train negatives using by appending flag --only_simulate_walks to binary create_dataset_arrays.py. For example, if you want to simulate walks for the PPI dataset (see datasets), then you can run the command:

python create_dataset_arrays.py --output_dir /path/to/asymproj/datasets/ppi --only_simulate_walks

The training binary deep_edge_trainer.py trains our model. There are many flags that customize the architecture, including size of node embedding (--embed_dim), latent dimensions of the deep neural network (--dnn_dims), and the low-rank projection dimension (--projection_dim). The dataset directory --dataset_dir must contain all files produced by create_dataset_arrays.py. During training, the trainer outputs the trained model onto subdirectory dumps. The name of the model files are automatically captured from the hyper-parameters (e.g. dimensions of embedding, dnn, projection). Setting flag --restore=0 will force to the trainer to start from scratch. Otherwise, if flag is ommitted, the trainer will continue training the model from the last saved state.

If you simulated walks on PPI, you can train a model with:

python deep_edge_trainer.py --dataset_dir /path/to/asymproj/datasets/ppi

The above command will print many lines like this:

@0 (790) test/train Best=0.80/0.85 cur=0.81/0.84. - test.d100_f100x100_g32

where @0 is epoch 0, 790 is the batch ID, and the metrics Best=0.80/0.85 and cur=0.81/0.84, respectively, are the best and current accuracies like test/train accuracies. The Best is taken for best train. We perform model selection at the training set. In other words, we select model parameters at peak train accuracy. Please view the flags of deep_edge_trainer.py to customize model hyper-parameters.