static error_aggregator map(icontext_type& context, const graph_type::edge_type& edge) {
error_aggregator agg;
if(edge.data().role == edge_data::TRAIN) {
agg.train_error = extract_l2_error(edge); agg.ntrain = 1;
} else if(edge.data().role == edge_data::VALIDATE) {
agg.validation_error = extract_l2_error(edge); agg.nvalidation = 1;
}
return agg;
}
map_join_pair collect_map (const graph_type::vertex_type& center,
graph_type::edge_type& edge,
const graph_type::vertex_type& other) {
map_join_pair ret;
if (edge.data().role == edge_data::TRAIN) {
ret.first.data[other.id()] = edge.data().obs; // save the old rating
} else {
// use prediction
double pred = center.data().factor.dot(other.data().factor);
ret.second.data[other.id()] = pred; // save the prediction
}
return ret;
}
/**
* \brief Get the other vertex in the edge.
*/
inline graph_type::vertex_type
get_other_vertex(const graph_type::edge_type& edge,
const graph_type::vertex_type& vertex) {
return vertex.id() == edge.source().id()? edge.target() : edge.source();
}
/**
* \brief Given an edge compute the error associated with that edge
*/
double extract_l2_error(const graph_type::edge_type & edge) {
const double pred =
edge.source().data().factor.dot(edge.target().data().factor);
return (edge.data().obs - pred) * (edge.data().obs - pred);
} // end of extract_l2_error
