code: public static int cuGraphGetRootNodes(CUgraph hGraph, CUgraphNode rootNodes[], long numRootNodes[]) 
      {
          return checkResult(cuGraphGetRootNodesNative(hGraph, rootNodes, numRootNodes));
      }
docs: Returns a graph's root nodes.<br>
  <br>
  Returns a list of \p hGraph's root nodes. \p rootNodes may be NULL, in which case this
  function will return the number of root nodes in \p numRootNodes. Otherwise,
  \p numRootNodes entries will be filled in. If \p numRootNodes is higher than the actual
  number of root nodes, the remaining entries in \p rootNodes will be set to NULL, and the
  number of nodes actually obtained will be returned in \p numRootNodes.
  
  @param hGraph       - Graph to query
  @param rootNodes    - Pointer to return the root nodes
  @param numRootNodes - See description
  
  @return
  CUDA_SUCCESS,
  CUDA_ERROR_DEINITIALIZED,
  CUDA_ERROR_NOT_INITIALIZED,
  CUDA_ERROR_INVALID_VALUE
  
  @see
  JCudaDriver#cuGraphCreate
  JCudaDriver#cuGraphGetNodes
  JCudaDriver#cuGraphGetEdges
  JCudaDriver#cuGraphNodeGetType
  JCudaDriver#cuGraphNodeGetDependencies
  JCudaDriver#cuGraphNodeGetDependentNodes