Dynamic Vertex Data

Introduction

Now you can also use dynamic chivectors as your vertex-data type. The basic usage is similar to Dynamic-Edge-Data, so please read that tutorial first.

Usage

There is currently no example application which uses dynamic vertex data, but there is a test code that does: http://code.google.com/p/graphchi/source/browse/src/tests/test_dynamicedata_loader.cpp

To enable dynamic vertex data, you need to define in the beginning of your source code:

  #define DYNAMICVERTEXDATA 1   

Then define the vertex datatype: typedef chivector<size_t> VertexDataType;

You can replace size_t with any primitive or struct type.

Here is example how to add and read values from the vertex's vector:

        chivector<size_t> * vvector = vertex.get_vector();
         int numitems = vertex.id() % 10;
         for(int i=0; i<numitems; i++) {
             vvector->add(i); // Arbitrary
         }
        
         /* Check vertex data immediatelly */
         for(int i=0; i<numitems; i++) {
            assert(vvector->get(i) == i);
         }

No, that instead of get_data(), you call get_vector() for the vertex object.

Accessing vertex data after computation

After your computation has finished, you can access the vertex values by using vertex-data iterator callback.

Here is example:

    VertexValidator validator;
    foreach_vertices(filename, 0, engine.num_vertices(), validator);

Here validator is a callback object:

class VertexValidator : public VCallback<chivector<size_t> > {
public:
    virtual void callback(vid_t vertex_id, chivector<size_t> &vec) {
        int numitems = vertex_id % 10;
        assert(vec.size() == numitems);
        
        for(int j=0; j < numitems; j++) {
            size_t x = vec.get(j);
            assert(x == j);
        }
    }
};

For example, if you want to output your results into a text-file, you simply implement file writing inside the callback.