still don't quite understand what batch is in 1dfft

I set an a(n), and let a(1:n/2) and a(n/2+1:n) be the same value. Then I made a cufftplan and called cufftExecZ2Z(a,n/2,1,2). Here the last 2 is the value of batch. Does the call mean the two halves of a are being transformed independently? If so, the returned array shold also have 2 same halves, which is not so in my case. I also tried cufftExecZ2Z(a,n,1,1) twice, and the returned array is just the same as calling cufftExecZ2Z(a,n,1,1) once. Then what does batch really mean?! Thanks!

I’ve found out the reason… I didn’t allocate eough memory in gpu…