Peregrine is an efficient, single-machine system for performing data mining tasks on large graphs. Some graph mining applications include:

• Finding frequent subgraphs
• Generating the motif/graphlet distribution
• Finding all occurrences of a subgraph

Peregrine is highly programmable, so you can easily develop your own graph mining applications using its novel, declarative, graph-pattern-centric API. To write a Peregrine program, you describe which graph patterns you are interested in mining, and what to do with each occurrence of those patterns. You provide the what and the runtime handles the how.

For full details, you can read our paper published in EuroSys 2020 or the longer version on arXiv.

TL;DR: compared to other state-of-the-art open-source graph mining systems, Peregrine:

• executes up to 700x faster
• consumes up to 100x less memory
• scales to 100x larger data sets
• on 8x fewer machines
• with a simpler, more expressive API

1. Quick start
2. Writing your own programs
3. Data graphs
4. Reproducing our EuroSys 2020 paper results
5. Contributing
6. Acknowledgements
7. Resources

Peregrine has been tested on Ubuntu 18.04 and Arch Linux but should work on any POSIX-y OS. It requires C 20 support (GCC version >= 9.2.1). Additionally, the tests require UnitTest .

To build Peregrine:

$ git clone https://github.com/pdclab/Peregrine.git
$ cd Peregrine
$ source tbb2019/bin/tbbvars.sh intel64
$ make -j
$ bin/test

Several sample applications, query patterns, and a sample dataset are released with the code. Calling any of the applications without arguments will show you what they expect:

$ bin/count
USAGE: bin/count <data graph> <pattern | #-motifs | #-clique> [# threads]

These applications print their results in <pattern>: <aggregation value> format.

For example, motif-counting:

$ bin/count data/citeseer 3-motifs 8
Counting 3-motifs
Finished reading datagraph: |V| = 3264 |E| = 4536
[...]
All patterns finished after 0.030265s
[2-3][1-3]: 23380
[1-2][1-3][2-3]: 1166

The string [2-3][1-3] encodes the pattern consisting of edges (1, 3), (2, 3), and 23380 is the number of unique occurrences Peregrine found in the citeseer graph.

Other applications give similar output:

$ bin/count data/citeseer 4-clique 8
[...]
All patterns finished after 0.030265s
[3-4][1-2][1-3][1-4][2-3][2-4]: 255
$
$ bin/count data/citeseer query/p1.graph 8
[...]
All patterns finished after 0.003368s
[3-4][1-2][1-3][1-4][2-3]: 3730

FSM provides support values instead of counts:

$ bin/fsm data/citeseer 3 300 8 # size 3 FSM with support 300
[...]
Frequent patterns:
[1,0-2,0][1,0-3,0][2,0-4,0]: 303
[1,1-2,1][1,1-3,1][2,1-4,1]: 335
Finished in 0.078629s

The existence-query application simply states whether the desired pattern exists or not:

$ bin/existence-query data/citeseer 14-clique 8
[...]
All patterns finished after 0.005509s
[pattern omitted due to length] doesn't exist in data/citeseer

In Peregrine's programming model, you provide a data graph, a set of patterns you're interested in, and a callback the system will apply to each occurrence of these patterns in your data graph. We present a brief overview of the API here, beginning with constructing patterns.

For all of the following code snippets, assume we are using namespace Peregrine.

Pattern graphs can constructed in two ways using the SmallGraph data structure:

Given a file in the following edge-list format:

<vertex-id> [label] <vertex-id> [label]

where the label's are optional 32-bit integers. To indicate a vertex is unlabelled in a partially-labelled pattern, assign it label -1. To indicate an anti-edge, any extra non-whitespace character can be placed at the end of the line.

For example, a triangle:

1 2
1 3
2 3

A vertex-induced 3-star, notice the last edge is an anti-edge:

1 2
1 3
2 3 -

A partially-labelled triangle (vertex 3 is unlabelled):

1 100 2 101
1 100 3 -1
2 101 3 -1

Then, construct the SmallGraph:

SmallGraph p("pattern_graph.txt");

Construct an empty graph and add edges/anti-edges one by one:

SmallGraph p
  .add_edge(1, 2)
  .add_edge(1, 3)
  .add_anti_edge(2, 3)
  .set_label(1, 100)
  .set_label(2, 101)
  .set_label(3, -1);

The PatternGenerator class is useful for

Quickly generating common patterns:

SmallGraph triangle = PatternGenerator::clique(3);
SmallGraph wedge = PatternGenerator::star(3);

Quickly generating many patterns:

int size = 4;
std::vector<SmallGraph> vertex_induced = PatternGenerator::all(size,
        PatternGenerator::VERTEX_BASED,        // 4 vertices
        PatternGenerator::INCLUDE_ANTI_EDGES); // anti-edges are inserted between all unadjacent vertices

std::vector<SmallGraph> vertex_induced_edge_based = PatternGenerator::all(size,
        PatternGenerator::EDGE_BASED,          // 4 edges
        PatternGenerator::INCLUDE_ANTI_EDGES); // anti-edges are inserted between all unadjacent vertices

std::vector<SmallGraph> edge_induced = PatternGenerator::all(size,
        PatternGenerator::EDGE_BASED,          // 4 edges
        PatternGenerator::EXCLUDE_ANTI_EDGES); // no extra anti-edges are inserted

std::vector<SmallGraph> edge_induced_vertex_based = PatternGenerator::all(size,
        PatternGenerator::VERTEX_BASED,        // 4 vertices
        PatternGenerator::EXCLUDE_ANTI_EDGES); // no extra anti-edges are inserted

Extending existing patterns:

std::vector<SmallGraph> vertex_extensions = PatternGenerator::extend({triangle}, PatternGenerator::VERTEX_BASED);
std::vector<SmallGraph> edge_extensions = PatternGenerator::extend({triangle}, PatternGenerator::EDGE_BASED);

Data graphs can be constructed from a preprocessed edge-list (see Data graphs) or a SmallGraph.

DataGraph dg("preprocessed_data/");

SmallGraph g("small_data_graph.txt");
DataGraph dg(g);

Pattern matching is done through the match and count functions.

Counting instances of patterns is very simple. Consider the following minimal motifs program:

#include "Peregrine.hh"
using namespace Peregrine;
void motifs(int size)
{
  int nthreads = 16;
  DataGraph g("data/citeseer/");

  auto patterns = PatternGenerator::all(size, PatternGenerator::VERTEX_BASED, PatternGenerator::INCLUDE_ANTI_EDGES);

  auto results = count(g, patterns, nthreads);

  for (const auto &[pattern, count] : results)
  {
    std::cout << pattern << ": " << count << std::endl;
  }
}

The arguments to count are straightforward: the data graph you wish to use, the patterns whose instances you wish to count, and the number of worker threads to use.

For arbitrary aggregations, use the match template function. For example, you could replace count above with this snippet (note that using count will be faster):

  const auto callback = [](auto &&handle, auto &&match) { handle.map(match.pattern, 1); };
  auto results = match<Pattern, uint64_t, AT_THE_END, UNSTOPPABLE>(g, patterns, nthreads, callback);

First, let's explain the template arguments to match:

• Peregrine::Pattern is the aggregation key type
• uint64_t is the aggregation value type
• AT_THE_END describes when aggregation happens: either AT_THE_END of execution or ON_THE_FLY
• UNSTOPPABLE indicates that you will not be using early termination

The regular parameters are the same as the count example except for callback. This is a function that will be called on each match for a pattern. It takes two arguments: a handle to Peregrine's aggregator, and the match itself.

Here, callback is mapping the pattern of the match to 1. Note that this lines up with the types passed to match: the aggregation key is Pattern and the value is an integer. Peregrine automatically takes care of simple types like uint64_t, aggregating them with the built-in sum operator.

Using more complicated aggregation values requires them to implement a few methods and implement a view function. The sample FSM application is a great example: check out both apps/fsm.cc and apps/Domain.hh to see a view function and the aggregation value methods.

Users can call three methods on the handle:

• map(key, value): maps key to value
• read_value(key): returns a view of the value mapped by key
• stop(): halts exploration early

Peregrine's data processor ingests graph edge-lists and stores them in binary adjacency-list format. For labeled data graphs, a separate file of vertex-label pairs is used. Both vertex ID's and labels should be 32-bit integers.

Edge-list file format:

<vertex-id> <vertex-id>

Label file format:

<vertex-id> <label>

Given such files edges.txt and labels.txt, with maximum vertex ID N, the processor is used as follows:

$ cd Peregrine
$ mkdir data/my-graph
$ make convert_to_binary
$ bin/convert_to_binary.sh edges.txt labels.txt N data/my-graph/

To convert an unlabeled dataset, labels.txt can be omitted.

See the guide.

A sincere thank you for deciding to spend your valuable time on this project! PR's are welcome, and will be carefully considered so long as they do not degrade performance or compromise correctness.

If you want to understand the system, the most important bits are in:

1. Peregrine.hh, which contains the main entry-points to the system
2. PatternMatching.hh, which contains the pattern matching engine
3. Graph.hh, where pattern analysis happens

You can also contribute in several ways without having to dig into Peregrine internals:

• Submit your applications to be included as samples
• Point out or improve missing or unsatisfactory documentation
• Complain about confusing errors
• Suggest features you wish Peregrine had
• Report correctness or performance bugs

We are grateful for the other open-source projects this codebase relies on:

• bliss
• Roaring

If you use this software project, please cite:

@inproceedings{10.1145/3342195.3387548,
  author = {Jamshidi, Kasra and Mahadasa, Rakesh and Vora, Keval},
  title = {Peregrine: A Pattern-Aware Graph Mining System},
  year = {2020},
  isbn = {9781450368827},
  publisher = {Association for Computing Machinery},
  address = {New York, NY, USA},
  url = {https://doi.org/10.1145/3342195.3387548},
  doi = {10.1145/3342195.3387548},
  booktitle = {Proceedings of the Fifteenth European Conference on Computer Systems},
  articleno = {Article 13},
  numpages = {16},
  location = {Heraklion, Greece},
  series = {EuroSys ’20}
}