Dear @Dezheng.Zhu ,
An error regarding “allocating space” has been discussed before on this forum, e.g., see: http://forums.nrel.gov/t/problems-in-test-in-fast-8/1868/2 .
If you are not already, I would recommend using the standard 64-bit version of OpenFAST (not 64-bit with double precision). Unless the problem is that you simply don’t have enough RAM available on your computer, in which case decreasing the discretization of the model (e.g., reducing the number of hydrodynamic analysis nodes) would probably help.
Best regards,