def ifft(f,gamma=0.,delta=0.,scale=1.):
from numpy import sqrt, roll, arange, exp, sign
from numpy.fft import ifft as ift
from scipy import pi
from spyctral.common.indexing import integer_range
from connection import int_connection_backward
try:
from pymbolic.algorithm import ifft
except:
from numpy.fft import ifft
N = f.size
ks = integer_range(N)
fx = int_connection_backward(f,0,0,gamma,delta)
flags = ks!=0
flags2 = ((ks%2)==1)
fx[flags2] *= -1
fx[flags] /= exp(-1j*ks[flags]*pi/N)
fx = roll(fx,-(N-1)/2)
if fx.dtype==object:
import pymbolic.algorithm as pyalg
return 1/sqrt(2*pi)*pyalg.sym_fft(fx,sign=-1)
else:
return N/float(sqrt(2*pi)*ift(fx))
def ifft_online(f,overhead):
from numpy.fft import ifft as ift
from numpy import roll
from connection import int_connection_backward_online
try:
from pymbolic.algorithm import fft
except:
from numpy.fft import fft
fx = int_connection_backward_online(f,overhead[1])
fx /= overhead[0]
N = fx.size
fx = roll(fx,-(N/2))
if fx.dtype==object:
import pymbolic.algorithm as pyalg
return pyalg.sym_fft(fx,sign=-1)/float(N)
else:
return ift(fx)