Igor Schein on Sun, 29 Nov 1998 12:39:37 -0500 |
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Discriminant of non-monic polynomials |
Hi, I've encountered several problems with poldisc and nfdisc commands. Here's the demonstration: ------------------------------------------------------------------------------ ? g(pol)=subst(pol,x,2*x+1) \\ If pol is f(x) then g(pol) is f(2*x+1) ? poldisc(g(polcyclo(57))) *** Warning: normalizing a polynomial with 0 leading term. *** bus error: bug in GP (please report). ? nfdisc(g(x^12-x-1)) *** impossible assignment I-->S ? nfdisc(g(polcyclo(23))) *** the PARI stack overflows !!! *** Warning: doubling stack size; new stack = 8000000. ? nfdisc(g(polcyclo(23))) *** the PARI stack overflows !!! *** Warning: doubling stack size; new stack = 16000000. \\keeps doubling until memory is exhausted ------------------------------------------------------------------------------ ??nfdisc tells me "preferably monic". How do I interprete this? Does it mean that nfdisc will give reliable output only for monic polynomials? ??poldisc on the other hand doesn't impose any restrictions on the input, so the first one must be a true bug. Thanks Igor