|Bill Allombert on Fri, 12 Aug 2011 11:26:32 +0200|
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|Re: polroots: impossible inverse|
On Fri, Aug 12, 2011 at 03:16:28PM +0800, Gordon Royle wrote: > I have just compiled Pari/GP for Mac OS X (10.7) from source. > > When I try > > p = 0+(0*x^0)+(0*x^1)+(11*x^2)+(-25*x^3)+(20*x^4)+(-7*x^5)+(1*x^6); > polrootsâ > > I get > > ? polroots(p) > *** at top-level: polroots(p) > *** ^----------- > *** polroots: impossible inverse modulo: Mod(4, 27457). > *** Break loop: type 'break' to go back to GP > > > Why is this? Every new Mac OS X major release comes with a broken compiler. This one generates wrong code for the modular inverse code. To work around this problem, you can do: rm Odarwin-i386/mp.o; make -C Odarwin-i386 gp CFLAGS="-O0 -fno-strict-aliasing" but you will get a slow binary. Better is to install gcc 4.5 and use it instead. Cheers, Bill. PS: please note the new list address.