Le forum de XCAS

Hi, Is there any guideline for citing giac and giacpy? I am trying to write a manuscript on sum of squares of rational polynomials (Sturmfel's problem) and need giac and giacpy for many of my computations. I would like to cite giac (and giacpy) for this. I understand Magma and GAP have their guideli...

@lukamar Thank you for considering nauty implementation. I will certainly be very interested if this is done. Currently I am using nauty in C++ which is much faster than using it in XCas and giac. But for minor computations and computations involving multiple CAS and giacpy I will be interested in u...

Hi, The command simult seems to only work on a square-system. So simult(A,b) will only deliver an answer if A is a square matrix. Is there possibly an option that makes it work if A is not a square matrix (similar to linsolve , but I do not want to create the linear equations to use linsolve here)? ...

Run proot(expression,n) where n is an integer for more precision. Nice one! Thanks. I have more precision now :) . BTW, can you remind me again how to express a symbol "x" as an algebraic element corresponding to a root (modulo conjugate) of a polynomial. I forgot this. So for instance I want to us...

Hi, It seems that giacpy only gives me python float precision when solving numerical values (eg. with proot and froot). Consider the following code from giacpy import giac, proot giac("printpow(1)") giac("Digits := 38") giac("Digits") #tells me if giac indeed set the precision to 38 digits #outputs ...

Hi, In giac if I have a polynomial with multiple roots, I also get multiple roots with proot (I cannot rely on root etc. because my polynomials have generally large degrees). This often leads to problem in my program. So I need to convert the output root into a set (python type) or something that wi...

Hi Bernard, Thank you for the suggestion. I realized there was rootof after my post. But I am not sure what to do with it alone if I want to get all the roots (exact solutions), because I really need these roots for another computation (so not only one of the roots, r:=rootof(g)). The only way I can...

Hi, Consider g:=x^6+x^4+x+2 rts:=roots(g) In my current version of XCas I get the warning Warning! Algebraic extension not implemented yet for poly [1,0,1,0,0,1,2] So my impression is that XCas/giac will not save these values as some algebraic numbers (exact roots) and my fear is that if I continue ...

@lukamar: Sorry for the late reply. I do not know about the paper you cite (apparently by microsoft researchers). But I know that the algorithms of McKay are trusted and cited regularly by graph-theorists. His C++ package (nauty) is very light-weight and has absolutely no dependencies whatsoever (I ...

@lukamar: I think this is a great development. Thank you for the implementation.

Is there an implementation for checking isomorphic graphs as well? If so, any way to compare it with known implementations (e.g. naughty).

Jose

Hi, How do you evaluate a symbolic expression in C++? If I do this giac::gen dbg("1+1",&ct); dbg = giac::eval(dbg, &ct); cout << gen2string(dbg) << endl; I correctly get "2" But if I do this: giac::gen dbg("x+2*x",&ct); dbg = giac::eval(dbg, &ct); cout << gen2string(dbg) << endl; I still get "x+2*x"...

Looking at the callers of Add_gen, it seems that the test will never be true, but I don't want to change the code. There is probably a define for visualc++ to avoid this additional (stupid) check. No problem, I understand that this is very sensitive so we do not want to break the code. I was able t...

I don't understand why there would be a problem, a, a_end etc. are std::vector< monomial<gen> >::const_iterator, new_coord is a std::vector< monomial<gen> >, therefore comparing a to new_coord.begin() makes sense. I think this is compiler/linker dependent (unfortunately this can be noticed as late ...

The forum will move to a new hardware/latest version of phpbb in a few days (or maybe weeks), it's not worth making changes here now... Ah ok. Wonderful, thanks for informing. I tried to continue with my debugging. I had to remove GIAC_VECTOR in my preprocessor because I think I could get to the ca...

Hi Bernard, I am not getting any wiser with debugging. But maybe there is a clue. I have noticed that in visual studio the preprocessor definition IMMEDIATE_VECTOR is used, is this relevant? Jose PS: Would it be possible for the admin of this forum to allow writing inline code. Sometimes writing a c...