fixed a bug with nfft==1

and added utility for more testing

test/compfft.py

@@ -0,0 +1,83 @@
+#!/usr/local/bin/python2.3
+
+# use FFTPACK as a baseline
+import FFT
+from Numeric import *
+import math
+import random
+import sys
+import struct
+
+pi=math.pi
+e=math.e
+j=complex(0,1)
+lims=(-32768,32767)
+
+def randbuf(n,cpx=1):
+    res = array( [ random.uniform( lims[0],lims[1] ) for i in range(n) ] )
+    if cpx:
+        res = res + j*randbuf(n,0)
+    return res
+
+def main():
+    from getopt import getopt
+    import popen2
+    opts,args = getopt( sys.argv[1:],'u:n:Rt:' )
+    opts=dict(opts)
+
+    util = opts.get('-u','./kf_float')
+
+    try:
+        n = int(opts['-n'])
+        cpx = opts.get('-R') is None
+        fmt=opts.get('-t','f')
+    except KeyError:
+        sys.stderr.write("""
+        usage: compfft.py 
+        -n nfft
+        -u utilname : see sample_code/fftutil.c
+        -R : real-optimized version
+        """)
+
+    x = randbuf(n,cpx)
+
+    cmd = '%s -n %d ' % ( util, n )
+    if cpx:
+        xout = FFT.fft(x)
+    else:        
+        cmd += '-R '
+        xout = FFT.real_fft(x)
+
+    proc = popen2.Popen3( cmd , bufsize=len(x) )
+
+    proc.tochild.write( dopack( x , fmt ,cpx ) )
+    proc.tochild.close()
+    xoutcomp = dounpack( proc.fromchild.read( ) , fmt ,1 )
+
+    sigpow = sum( xout * conjugate(xout) )
+    print len(xout)
+    print len(xoutcomp)
+    
+    diff = xout-xoutcomp
+    noisepow = sum( diff * conjugate(diff) )
+
+    snr = 10 * math.log10(abs( sigpow / noisepow ) )
+    print 'NFFT=%d,SNR = %f dB' % (n,snr)
+
+def dopack(x,fmt,cpx):
+    if cpx:
+        s = ''.join( [ struct.pack('ff',c.real,c.imag) for c in x ] )
+    else:
+        s = ''.join( [ struct.pack('f',c) for c in x ] )
+    return s 
+
+def dounpack(x,fmt,cpx):
+    uf = fmt * ( len(x) / 4 )
+    s = struct.unpack(uf,x)
+    if cpx:
+        return array(s[::2]) + array( s[1::2] )*j
+    else:    
+        return array(s )
+
+if __name__ == "__main__":
+    main()