I use subroutine newxyz to solve moving grid problem. But when I just want to calculate time step 1, it actually use newxyz two times, time step 0 and 1.

How could I just use newxyz one time?

I had the same problem. I simply added an "if" statement that checks for the iteration number: if iter=1 jumps the mesh modification. Cheers Roadracer

The code is designed to allow user to change the mesh from prostar to the proper positions at time=0. As Roadracer pointed out, you can either use if(iter.gt.0) or if (time.gt.0) to skip mesh change at time=0.