BUG: Corrected no-op in reverse transform multi-D fft - see #813

src/randomProcesses/fft/fft.C

@@ -185,18 +185,18 @@ void Foam::fft::transform
     const label N = field.size();
     fftw_complex in[N], out[N];
 
+    // If reverse transform : renumber before transform
+    if (dir == REVERSE_TRANSFORM)
+    {
+        fftRenumber(field, nn);
+    }
+
     forAll(field, i)
     {
         in[i][0] = field[i].Re();
         in[i][1] = field[i].Im();
     }
 
-    // If backward transform : renumber before transform
-    if (dir == FFTW_BACKWARD)
-    {
-        fftRenumber(field, nn);
-    }
-
     // Create the plan
     // FFTW_FORWARD = -1
     // FFTW_BACKWARD = 1