forward transform
.................\vfftpack
.................\........\pimach.f
.................\........\vcosqf.f
.................\........\vradf2.f
.................\........\vradf3.f
.................\........\vradf4.f
.................\........\vradf5.f
.................\........\vradfg.f
.................\........\vrfftf.f
.................\........\vrftf1.f
.................\........\vsinqf.f