On Thu, 2006-03-16 at 14:39 -0800, Eric Blossom wrote: > On Thu, Mar 16, 2006 at 05:24:26PM -0500, Charles Swiger wrote: > > On Thu, 2006-03-16 at 12:35 -0800, Eric Blossom wrote: > > > > > > Here's the only place they're used: > > > > d_freq = d_freq + d_beta * error; > > d_phase = mod_2pi(d_phase + d_freq + d_alpha * error); > > > > It's way over my head but is d_freq supposed to be in the d_phase > > calculation, 2nd line? phase is mod_2pi but freq can be a very big > > number, like mod_2pi(100000 + 1.572849). That is I'm USING very big > > numbers for max_freq and min_freq - don't suppose they're normalized > > somehow. > > OK. I can see why that would be a problem. mod_2pi is optimized for > the expected "close in case" (symmetric around zero), thus the phase > isn't *really* getting folded down to [-pi,pi]. > > Try changing mod_2pi to make the bounds check and then compute the > modulus if it needs to using division, floor, multiplication and > subtraction. It's not cheap, but it'll probably compute the right > answer.
Does anybody know how to fix this in c++ ? In PYTHON there's 'truncating divide' ( // ) where this seems to work: >>> M_PI = math.pi >>> M_TWOPI = 2 * math.pi >>> >>> def mod_2pi (num): ... if ( n > M_TWOPI ): ... return ( num - M_TWOPI * ( num // M_TWOPI )) ... elif ( n < -M_TWOPI ): ... return ( num + M_TWOPI * ( -num // M_TWOPI )) ... else: ... return num ... >>> num = 5000 * math.pi + 2.13 >>> mod_2pi(num) 2.1299999999991996 >>> num = 500000 * math.pi + 3.15 >>> mod_2pi(num) 0.0084073462057858706 >>> num = -500000 * math.pi - 3 >>> mod_2pi(num) -3.0 >>> num = -500000 * math.pi - 3.15 >>> mod_2pi(num) -0.0084073462057858706 How to translate into effecient C++ is beyond me at the moment (but googling around for a solution) --Chuck _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
