On Tue, Nov 19, 2013 at 9:46 AM, Peter Mueller <ypf...@googlemail.com> wrote: > Dear Sage Developers, > > the Elias bound of coding theory is wrongly implemented. Compare >
Thanks for this report. Would you mind creating a trac ticket for this? I'd be very grateful. > sage: elias_upper_bound(10,2,8,algorithm="gap"), elias_upper_bound(10,2,8) > (4, 120) > > Looking at the relevant piece of code > > else: > def ff(n,d,w,q): > return r*n*d*q**n/((w**2-2*r*n*w+r*n*d)*volume_hamming(n,q,w)); > def get_list(n,d,q): > I = [] > for i in range(1,int(r*n)+1): > if i**2-2*r*n*i+r*n*d>0: > I.append(i) > return I > I = get_list(n,d,q) > bnd = min([ff(n,d,w,q) for w in I]) > return int(bnd) > > reveals the mistake: The `return I' is one tab too deep, it has to get > executed after the for loop is finished. > > One other note, which also refers to the otherwise correct algorithm="gap" > version: Something like elias_upper_bound(10,2,1) yields an error because > for these parameters the Elias bound is not defined. Wouldn't it be better > to return some trivial but true result in this case, like q^n? > > Yet another question: Does the above example, where two functions get > defined but each of them gets used only at one place, follow certain coding > conventions? As a work around, I implemented the Elias bound as > > t = n*(1-1/q) > lr = [(r,r^2-2*t*r+t*d) for r in [1..floor(t)]] > lv = [t*d*q^n/z/volume_hamming(n,q,r) for (r,z) in lr if z > 0] > return q^n if len(lv) == 0 else floor(min(lv)) > > which looks cleaner to me. > > Best wishes, > Peter M. > > > > > > > > -- > You received this message because you are subscribed to the Google Groups > "sage-support" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to sage-support+unsubscr...@googlegroups.com. > To post to this group, send email to sage-support@googlegroups.com. > Visit this group at http://groups.google.com/group/sage-support. > For more options, visit https://groups.google.com/groups/opt_out. -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/groups/opt_out.
