`std::hash<int>` doesn't hash, it just returns the int. So this code has a collision when dim[0] is 1 and 32. https://github.com/flexflow/FlexFlow/blob/3a825ed6ae7425ea3578006e458cfcaf19e038a5/src/runtime/machine_view.cc#L49-L59 Solution is to use hash_combine in hash_utils.h.