the standard definition of the Riemannian diameter of a setAin the setB⊇A, where bothAandBare subsets of a Riemannian manifold (M,g)(2.1)diam(A,B) := supx,y∈Ainfγ:[0,1]→Bγ(0)=x,γ(1)=y∫10| ̇γ(s)|gds.