A surgical pelvic drill for operating hip osteoarthritis adapted to create a hole in the pelvic bone of a human patient is provided. The dissimilarity or similarity between nodes at the two ends of the edge is used as the feature amount of the edge, and the edge is classified into one of a plurality of classes based on the feature amount. The monolithic structure includes a straight flow tube and a cavity separated from the flow tube, where a shared wall part forms part of the wall of the flow tube and of an inside surface of the cavity.