docs/libraries/cpp/examples/snap-to-graphar.md

# Convert SNAP Datasets to GraphAr Format

[SNAP](https://snap.stanford.edu/data/) (Stanford Network Analysis
Project) is a general-purpose network analysis and graph mining library.
It provides a variety of datasets for research and development. In this
section, we will show how to convert the SNAP datasets to GraphAr
format, showcasing the process with the
[ego-Facebook](https://snap.stanford.edu/data/ego-Facebook.html) graph
as a case study. The conversion leverages GraphInfo constructors and the
high-level writer functions from the C++ library.

## Prepare the SNAP Dataset

Before converting, download the ego-Facebook dataset from the SNAP
website. The dataset is a text file with each line representing an edge
in the graph.

```bash
cd /path/to/your/dataset
wget https://snap.stanford.edu/data/facebook_combined.txt.gz
gunzip facebook_combined.txt.gz
```

## Convert the SNAP Dataset to GraphAr Format

The initial phase involves constructing VertexInfo, EdgeInfo, and
GraphInfo objects, which are subsequently serialized into YAML files.
For instance, the code snippet below illustrates the creation and
storage of the vertex information file.

```cpp
auto version = graphar::InfoVersion::Parse("gar/v1").value();

// meta info
std::string vertex_type = "node", vertex_prefix = "vertex/node/";

// create vertex info
auto vertex_info = graphar::CreateVertexInfo(
    vertex_type, VERTEX_CHUNK_SIZE, {}, vertex_prefix, version);

// save & dump vertex info
ASSERT(!vertex_info->Dump().has_error());
ASSERT(vertex_info->Save(save_path + "node.vertex.yml").ok());

// create and save edge info file ...
auto edge_info = ...
ASSERT(!edge_info->Dump().has_error());
ASSERT(edge_info->Save(save_path + "node_links_node.edge.yml").ok());

// create and save graph info file ...
auto graph_info = ...
ASSERT(!graph_info->Dump().has_error());
ASSERT(graph_info->Save(save_path + graph_name + ".graph.yml").ok());
```

Subsequently, we employ the high-level vertex and edge builders provided
by the GraphAr C++ library to generate payload data files with vertex
and edge data. The code snippet that follows demonstrates the generation
and preservation of the edge data file.

```cpp
// construct edges builder
auto e_builder = graphar::builder::EdgesBuilder::Make(
                     edge_info, save_path, ADJLIST_TYPE, VERTEX_COUNT)
                     .value();
// read edge data from file
std::ifstream file(DATA_PATH);
std::string line;
while (std::getline(file, line)) {
  std::istringstream iss(line);
  // skip comments
  if (line[0] == '#') {
    continue;
  }
  int src, dst;
  if (!(iss >> src >> dst)) {
    break;
  }
  graphar::builder::Edge e(src, dst);
  ASSERT(e_builder->AddEdge(e).ok());
}

// dump & clear
ASSERT(e_builder->Dump().ok());
e_builder->Clear();
```

For comprehensive insights into this example, please consult the
accompanying [source
code](https://github.com/apache/incubator-graphar/tree/main/cpp/examples/snap_dataset_to_graphar.cc)
.