ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Sat, 27 Mar 2021 14:54:58 +0100Goppa Codes: Cannot create decoder with large parametershttps://ask.sagemath.org/question/56410/goppa-codes-cannot-create-decoder-with-large-parameters/ Hello,
I've been playing around with linear error-correcting codes with the intention of programming a demonstration of McEliece's Cryptosystem, which utilises Goppa codes.
I've been following the format outlined in the SAGE tutorial. I can't post the link for some reason, but it can be found by searching "sagemath Goppa codes". I have no issue running the following code to create a Goppa code over field GF(2^4) and its corresponding decoder.
F = GF(2^4)
R.<x> = F[]
g = x^2+x+1
L = [a for a in F.list if g(a) != 0]
C = codes.GoppaCode(g,L)
D = C.decoder()
However, the cryposystem I'm trying to program requires parameters higher than this, specifically over the field of GF(2^10). The code that I've used to create this Goppa code and its decoder are therefore as follows.
F = GF(2^10)
R.<x> = F[]
g = x^50+x^3+1
L = [a for a in F.list if g(a) != 0]
C = codes.GoppaCode(g,L)
D = C.decoder()
This creates a [1024, 524] Goppa code over GF(2) and there's no issue in generating the code C, or even using it to encode a message vector (of length 524).
Unfortunately, I seem to encounter a memory issue when I run the final line to create the decoder D. My initial response was to try it on a machine with larger memory (64GB), but I had no luck there. I assume it's because the code that I'm trying to create is pretty huge, but it would be really helpful if there's somehow a way around the problem to allow me implement this Goppa code and generate its decoder.
Any help would be greatly appreciated and I'm happy to provide more details if needed.
Thank you very much!!StudentSat, 27 Mar 2021 14:54:58 +0100https://ask.sagemath.org/question/56410/Video for Sage Cell ---> Sage Cloud conversion?https://ask.sagemath.org/question/23519/video-for-sage-cell-sage-cloud-conversion/I was wondering if anyone has made a video to help students transition from using the Sage Cell Server (for simple tasks) to the Sage Cloud system?
I'm thinking of something very short, to give flavor and "the basics." Perhaps something 5-10 minutes long suitable for 200-level math, physics and engineering majors.Gregory BardMon, 21 Jul 2014 19:26:25 +0200https://ask.sagemath.org/question/23519/Sage for (very) undergrad studentshttps://ask.sagemath.org/question/8689/sage-for-very-undergrad-students/Hi all
Today I had hard time with Sage because
sage: f(x)=1/(1-x**2)
sage: g(x)=f.integrate(x)
sage: g(0.5)
0.549306144334055 - 1.57079632679490*I
sage: g
x |--> -1/2*log(x - 1) + 1/2*log(x + 1)
This is not the primitive my students are expecting : they expect 1-x on the denominator.
In particular they are not expecting :
sage: ln(-1)
I*pi
I had other some small problems like that with Sage like the difference between +Inf,-Inf and Inf when computing a limit (in the latter case my students are expecting "does not exist").
So my question is : is there a way to ask Sage to behave like a very undergrad student is expected to behave ? (ex : ln(-1) does not exist)
Is there a way to say «I'm an undergrad student and I want Sage to solve my homework of basics calculus» ?
Do you have experience/habits to prevent Sage to mislead students by its unexpected answers (however mathematically correct) ?
Laurent ClaessensThu, 02 Feb 2012 07:58:11 +0100https://ask.sagemath.org/question/8689/