Thank you very much for your prompt replies. I was sure that range(n) creates an iterator instead of the list itself, my bad. In any case, even if the function is creating this list, why is it still stored in memory after the function terminates? It is a local variable, and is not returned so it should be erased from the RAM.
In my original code, I iterate ternary polynomials over a finite field K and factor them. I am constructing them from the vector of the coefficients, which is an element of K^n. In order to create the vector of coefficients, I iterate over K^n (which I think should support iteration, as K does, but after the mistake on range I am no more so confident). Here an example: (actually it behaves badly even with binary polynomials): def ex_f(q): > > K = GF(q) > > P.<x,y,z> = PolynomialRing(K,3) > > monomials=[x,y,z,x^2,y^2,z^2] > > for v in K^6: > > f=1+sum([v*m for (v,m) in zip (v,monomials)]) > > f.factor() > > With 7 as input it uses 283MB. By uses, as above, I mean the output of the function "check_memory" which should return the difference of the amounts of RAM dedicated at the Sage process before and after launching ex_f(7). Running a similar function with univariate polynomials does not require memory, so I guess should not be an iterator-related problem. Il giorno venerdì 15 dicembre 2017 12:27:22 UTC, Dima Pasechnik ha scritto: > > > > On Friday, December 15, 2017 at 12:16:04 PM UTC, vdelecroix wrote: >> >> You can fill your memory with something simpler >> >> sage: l = range(10**9) >> >> As far as I can see it has nothing to do with Sage or loops. In Python2 >> the range functions constructs a list. And in the above example, the >> list is huge. >> > > indeed. In order to avoid this, use xrange() instead of range() > (well, this is not going to make your code Python3-proof, but range() in > Python3 > is what xrange() is in Python3; see e.g. > https://stackoverflow.com/a/15015199/557937 > on how to make it portable) > > > > >> >> Vincent >> >> On 15/12/2017 12:06, Marco Caselli wrote: >> > Hello there, >> > I am currently having trouble in memory management, I wrote a code that >> was >> > not supposed to store anything but actually it was using a massive >> amount >> > of memory. At a first glance, I thought it was related to some function >> in >> > my code, such as factor() for polynomials in a multivariate ring over a >> > finite field. I dug a bit deeper and the problem seems even at a lower >> > level: >> > >> > def check_memory(k): >> >> a=get_memory_usage() >> >> silly_function(k) >> >> return get_memory_usage()-a >> >> >> >> def silly_function(k): >> >> for i in range(10^k): >> >> 2+2 >> > >> > >> > Notice that silly_function does not store neither return anything, so >> the >> > memory usage should be zero. >> > check_memory(9) returned 23446.37109375, this amount is in MB, so those >> are >> > 23GB. This information is consistent with the data from top. At a >> second >> > run it returned just 972.62109375, which is still a lot. >> > >> > -- 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 https://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
