Schematically:
FuncNgbOp2dExtraDispatch  -->  _Row(P1,Cnum)  -->  _Pix_P1Cnum
                            |
                            |
                            +->  _Row(P1,Loop)  -->  _Pix_P1Loop
                            |                    /
                            +->  _Row(P2,Loop)  -->  _Pix_P2Loop
                            |
                            +->  _Row(PN,Loop)  -->  _Pix_P1Loop
 1.5.1