  Kim, Kresch and Oh defined unramified Gromov-Witten invariants. For a
threefold, Pandharipande conjectured that they are equal to Gopakumar-Vafa
invariants (BPS invariants) in the case of Fano classes and primitive
Calabi-Yau classes. We prove the conjecture using a wall-crossing technique.
This provides an algebro-geometric construction of Gopakumar-Vafa invariants in
these cases.
