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

src/randomProcesses/fft/fft.C

@@ -185,16 +185,16 @@ void Foam::fft::transform
     const label N = field.size();
     fftw_complex in[N], out[N];
 
-    forAll(field, i)
+    // If reverse transform : renumber before transform
+    if (dir == REVERSE_TRANSFORM)
     {
-        in[i][0] = field[i].Re();
-        in[i][1] = field[i].Im();
+        fftRenumber(field, nn);
     }
 
-    // If backward transform : renumber before transform
-    if (dir == FFTW_BACKWARD)
+    forAll(field, i)
     {
-        fftRenumber(field, nn);
+        in[i][0] = field[i].Re();
+        in[i][1] = field[i].Im();
     }
 
     // Create the plan