This is David Harvey trying to write stupid code, so in ordinary person terms that translates as pretty smart.
Bill. On 8 Apr, 10:03, John Cremona <john.crem...@gmail.com> wrote: > Surely it would be worth testing self.gcd(m)==m early on in the > exact_log function, i.e. that m divides self? I may be naive but I > would implement this by testing m|a, if so dividing a by m, and > continuing. The current method describes itself as "extremely stupid > code" but it still trying to be clever!. > > John > > 2009/4/8 Bill Hart <goodwillh...@googlemail.com>: > > > > > Here's some timings for exact_log: > > > In Sage: > > > def random(n): > > a = ZZ.random_element(n) > > return a > > > def z_exact_log_test(m, n, k): > > for i in range(0, m) : > > a = random(n) + 2 > > b = random(k) > > c = a^b > > d = c.exact_log(a) > > if b != d: > > print "Error", b, "!=", d > > > time z_exact_log_test(100000, 64, 1000) > > > 4.72s > > > In Magma: > > > t:=Cputime(); > > for i := 0 to 100000 do > > a := Random(64) + 2; > > b := Random(1000); > > c := a^b; > > d := Ilog(a,c); > > if d ne b then > > print "Error"; > > end if; > > end for; > > Cputime(t); > > > 0.72s > > > Bill. > > > On 8 Apr, 07:17, Bill Hart <goodwillh...@googlemail.com> wrote: > >> I've been looking through the methods for ZZ with a view to doing a > >> Magma/Sage comparison for marketing purposes. I've been noticing a few > >> issues as I go. There's going to be lots of these, so I think I should > >> give my list in small blocks. I can file trac tickets for them once > >> someone verifies that these are really not just me not knowing enough > >> python, or whatever. > > >> ZZ > >> ==== > > >> Speed Issues: > > >> * n.bits takes much longer than n.binary(), but the latter needs to > >> compute the former first!!! > >> * n.coprime_integers uses a hopelessly slow algorithm (we should at > >> least use a sieve) > >> * n.factor is bizarrely slow for small integers (e.g. n < 1,000,000) > >> by a HUGE factor > >> * n.exact_log can be done faster for small bases by making careful use > >> of the identity log_m(n) = log_2(n)/log_2(m) (I wrote a crappy broken > >> python implementation and timed this - I don't know how to write it > >> properly as I don't know enough about Sage yet) > > >> Missing doc strings: > > >> * n.base_extend > >> * n.additive_order > >> * n.category > >> * n.db (doesn't give an example) > >> * n.degree > > >> Missing methods: > > >> * n.euler_phi > >> * n.random (random integer less than n - I will believe you if you > >> tell me this is not the python way) > > >> Weird names: > > >> * n.divide_knowing_divisible_by (perhaps div_exact, exact_quotient, > >> divide_exact would be better) > > >> Documentation issues: > > >> * n.dump says "Same as self.save(filename, compress)", but compress is > >> not discussed in save docstring > > >> Bill. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to sage-devel@googlegroups.com To unsubscribe from this group, send email to sage-devel-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
