LongIterator neighbors = iterationStrategy.neighborIterator(buildContext, rowItem, false);
currentRow.fill(0);
// Compute similarities and populate the vector
while (neighbors.hasNext()) {
final long colItem = neighbors.nextLong();
final SparseVector vec2 = buildContext.itemVector(colItem);
assert currentRow.containsKey(colItem);
currentRow.set(colItem, similarity.similarity(rowItem, vec1, colItem, vec2));
}