Compare FFTW to CUFFT on HYAK. Measure and plot the performance of calculating the gradient

of a $3$D double complex plane wave defined on cubic lattices of dimension n $3$ from $163$ to n $=2563,$ stride n$=2$

for both the FFTW and CUDA FFT $($CUFFT$)$ implementations on HYAK. Let each n be measured ntrial times

and plot the average performance for each case versus n$,$ ntrial $3.$ Submit your performance plot which should

have $$FLOPs$$ on the y$-$axis $($or some appropriate unit of FLOPs$)$ and the dimension of the cubic lattices $($n$)$ on

the x$-$axis. You will need to estimate the operation count of computing the derivative using FFT on a lattice