On Sunday, January 4, 2015 8:12:10 AM UTC+1, Terry Reedy wrote: > On 1/3/2015 6:19 PM, austin aigbe wrote: > > > I am currently implementing the LTE physical layer in Python (ver 2.7.7). > > For the qpsk, 16qam and 64qam modulation I would like to know which is more > > efficient to use, between an integer comparison and a list comparison: > > > > Integer comparison: bit_pair as an integer value before comparison > > > > # QPSK - TS 36.211 V12.2.0, section 7.1.2, Table 7.1.2-1 > > def mp_qpsk(self): > > r = [] > > for i in range(self.nbits/2): > > bit_pair = (self.sbits[i*2] << 1) | self.sbits[i*2+1] > > if bit_pair == 0: > > r.append(complex(1/math.sqrt(2),1/math.sqrt(2))) > > elif bit_pair == 1: > > r.append(complex(1/math.sqrt(2),-1/math.sqrt(2))) > > elif bit_pair == 2: > > r.append(complex(-1/math.sqrt(2),1/math.sqrt(2))) > > elif bit_pair == 3: > > r.append(complex(-1/math.sqrt(2),-1/math.sqrt(2))) > > return r > > > > List comparison: bit_pair as a list before comparison > > > > # QPSK - TS 36.211 V12.2.0, section 7.1.2, Table 7.1.2-1 > > def mp_qpsk(self): > > r = [] > > for i in range(self.nbits/2): > > bit_pair = self.sbits[i*2:i*2+2] > > if bit_pair == [0,0]: > > r.append() > > elif bit_pair == [0,1]: > > r.append(complex(1/math.sqrt(2),-1/math.sqrt(2))) > > elif bit_pair == [1,0]: > > r.append(complex(-1/math.sqrt(2),1/math.sqrt(2))) > > elif bit_pair == [1,1]: > > r.append(complex(-1/math.sqrt(2),-1/math.sqrt(2))) > > return r > > Wrong question. If you are worried about efficiency, factor out all > repeated calculation of constants and eliminate the multiple comparisons. > > sbits = self.sbits > a = 1.0 / math.sqrt(2) > b = -a > points = (complex(a,a), complex(a,b), complex(b,a), complex(b,b)) > complex(math.sqrt(2),1/math.sqrt(2)) > def mp_qpsk(self): > r = [points[sbits[i]*2 + sbits[i+1]] > for i in range(0, self.nbits, 2)] > return r > > -- > Terry Jan Reedy
Cool. Thanks a lot. -- https://mail.python.org/mailman/listinfo/python-list
