代写代考

using FFTW

Copyright By PowCoder代写 加微信 powcoder

θ = range(0, 2π; length=n+1)[1:end-1]
Q = 1/sqrt(n) * [exp(-im*(k*θ[j])) for k=0:n-1, j=1:n]

b = randn(n)

norm(Q’b – sqrt(n)*ifft(b))

norm(Q*b – 1/sqrt(n)*fft(b))

2.999301662503971e-14

@time Q’b;

0.000017 seconds (3 allocations: 1.141 KiB)

@time ifft(b);

0.000062 seconds (35 allocations: 3.094 KiB)

b = randn(n)

@time ifft(b);

0.043449 seconds (37 allocations: 32.002 MiB)

n = 1_000_000
b = randn(n)

@time ifft(b);

0.036335 seconds (37 allocations: 30.520 MiB, 9.98% gc time)

程序代写 CS代考 加微信: powcoder QQ: 1823890830 Email: powcoder@163.com