On Aug 2, 6:41 pm, William Stein <wst...@gmail.com> wrote: > On Tue, Aug 2, 2011 at 9:51 AM, VictorMiller <victorsmil...@gmail.com> wrote: > > Yesterday I started up sage 4.6.2 on one of our compute servers, > > started the notebook interface, and connected to from firefox on my > > workstation. I started up a notebook session, where I constructed a > > particular elliptic curve over GF(2^351), and a point on it. I > > (unwisely) tried > > > P1.order() > > > When it didn't come back after 30 seconds or so, I realized that I was > > implicitly asking Sage to compute the order of the curve and then
As far as I recall, Sage does not have special code for computing elliptic curve group orders over such fields. Assuming that your curve's j-invariant is as bad as possible (of degree 351) then it will be finding the group order using a generic BSGS algorithm, which (as you know!) uses lots of space as well as time. But this does not explain why there are all the other processes. Anyway. E.order() itself might succeed and would not trigger factorization of the order, while P.order() would. The integer factorization would be done using (I think, someone could confirm) the pari library; and that might trigger child processes to start up. On my machine, for a random curve over GF(2^75), E.order() takes 18s while over GF(2^100) a random example takes 1123s. I'm not about to try GF(2^351)! John > > factor that order, so I tried to kill it by using Interrupt, which > > didn't work, so I restarted the worksheet. However, at that point > > things became non-responsive. I eventually ended up logging onto the > > server and stopping sage. About an hour later the computer > > administrator came into my office saying that I had nearly brought the > > compute server to its knees because I had started 1300 processes (all > > running something in the sage directory)! Has anybody seen anything > > like this before? > > I have definitely never heard of or seen anything like this before. > Is it something you can reproduce? -- You don't say above... > > This of course sounds like a "fork bomb". Note that many computer > systems are configured by default to not allow a single user to create > that many processes, in order to avoid fork bombs. You can use > ulimit to set a process limit on a per-session basis, if you want to > test this issue again on your computer without the possibility of > actually nearly bringing the computer to its knees. > > -- William > > > > > Victor > > > -- > > To post to this group, send email to sage-support@googlegroups.com > > To unsubscribe from this group, send email to > > sage-support+unsubscr...@googlegroups.com > > For more options, visit this group > > athttp://groups.google.com/group/sage-support > > URL:http://www.sagemath.org > > -- > William Stein > Professor of Mathematics > University of Washingtonhttp://wstein.org -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
