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n-dimensional FFT works

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This commit is contained in:
Mark Borgerding 2003-12-30 02:50:45 +00:00
parent 5e6199c868
commit 22ff70b71d
1 changed files with 43 additions and 16 deletions
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59
test/fft.py
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@ -148,9 +148,11 @@ def randmat( ndims ):
def test_fftnd(ndims=3):
import FFT
import Numeric
random.seed(2)
x=randmat( ndims )
print 'dimensions=%s' % str( Numeric.shape(x) )
#print 'x=%s' %str(x)
xver = FFT.fftnd(x)
x2=myfftnd(x)
err = xver - x2
@ -158,7 +160,11 @@ def test_fftnd(ndims=3):
xverf = flatten(xver)
errpow = Numeric.vdot(errf,errf)+1e-10
sigpow = Numeric.vdot(xverf,xverf)+1e-10
print 'SNR=%sdB' % str(10*math.log10(abs(sigpow/errpow) ) )
snr = 10*math.log10(abs(sigpow/errpow) )
if snr<80:
print xver
print x2
print 'SNR=%sdB' % str( snr )
def myfftnd(x):
import Numeric
@ -168,20 +174,41 @@ def myfftnd(x):
def fftndwork(x,dims):
import Numeric
if len(dims)==1:
return fft(x,0)
else:
samples_per_chunk = Numeric.product( dims[1:] )
precomp = [ ]
curfftlen = dims[ 0 ]
for i in range( curfftlen ):
xslice = x[ i*samples_per_chunk : (i+1)*samples_per_chunk ]
precomp.extend( fftndwork( xslice,dims[1:] ) )
xout = [ complex(0,0) ] * samples_per_chunk * dims[0]
for i in range( samples_per_chunk ):
pfx = fft( precomp[ i::samples_per_chunk ],0 )
xout[ i::samples_per_chunk ] = pfx
return xout
kk=1
for k in range( len(dims) ):
d=dims[ k ]
g=Numeric.product( dims ) / d
#print 'dimension %d==%d, g=%d' % ( k ,d,g )
#print 'x=%s' % str(x)
next_stage = []
chunk = 0
for ii in range(kk):
start = ii*d*g
for i in range(start,start+g):
xslice = x[i:(i+d)*g:g]
if len(xslice) != d:
print 'len(xslice)= %d' % len(xslice)
sys.exit(0)
fxslice = fft(xslice,0)
#print 'fft( x[%d:%d:%d] ) ' %( i,(i+d)*g,g),
#print 'fft( %s ) == %s ' % (str(xslice),str(fxslice))
next_stage.extend( fxslice )
if len(next_stage) != len(x):
print 'len(next_stage)= %d' % len(next_stage)
sys.exit(1)
#kk *= d
#print 'next_stage=%s' % str(next_stage)
x = next_stage[:]
return x
if __name__ == "__main__":
main()
try:
nd = int(sys.argv[1])
except:
nd=None
if nd:
test_fftnd( nd )
else:
sys.exit(0)