[GiNaC-devel] Factorization Bug

[Alexei Sheplyakov]

Dear Aless,

On Fri, May 14, 2010 at 10:21:09AM +0200, Aless Lasaruk wrote:

> i would like to report a bug in polynomial factorization.

 
> I want to factorize the following multivariate polynomial:
> 
> 792*z^8*w^4*x^3*y^4*u^7+24*z^4*w^4*x^2*y^3*u^4+264*z^8*w^3*x^2*y^7*u^5+198*z^4*w^5*x^5*y*u^6+110*z^2*w^3*x^5*y^4*u^6-120*z^8*w*x^4*u^6-480*z^5*w*x^4*y^6*u^8-720*z^7*x^3*y^3*u^7+165*z^4*w^2*x^4*y*u^5+450*z^8*w^6*x^2*y*u^8+40*z^2*w^3*x^3*y^3*u^6-288*z^7*w^2*x^3*y^6*u^6+250*z^6*w^4*x^2*y^4*u^8+576*z^7*w^7*x^2*y^4*u^8-80*z^6*w^2*x^5*y^3*u^7-144*z^8*w^4*x^5*u^7+120*z^4*w*x^2*y^6*u^6+320*z^5*w^5*x^2*y^7*u^8+192*z^7*w^6*x*y^7*u^6-12*z^4*w^3*x^3*y^5*u^6-36*z^4*w^4*x^4*y^2*u^8+72*z^4*w^5*x^3*u^6-20*z^2*w^2*x^4*y^5*u^8+660*z^8*w*x^2*y^4*u^6+66*z^4*w^4*x^4*y^4*u^4+440*z^6*w^2*x^3*y^7*u^7-30*z^4*w*x^3*y^2*u^7-48*z^8*w^3*x^4*y^3*u^5+72*z^6*w^2*x*y^6*u^4-864*z^7*w^3*x^4*y^3*u^8+480*z^7*w^4*x*y^4*u^7+60*z^4*w^2*x^2*u^5+375*z^8*w^3*x*y*u^7+150*z^8*w^5*x*y^4*u^6+180*z^6*x*y^3*u^5+216*z^6*w^3*x^2*y^3*u^6
> 
> GiNaC crashes with the following exception:
> 
> malloc: *** mmap(size=3774734336) failed (error code=12)
> *** error: can't allocate region
> *** set a breakpoint in malloc_error_break to debug
> terminate called after throwing an instance of 'std::bad_alloc'
>   what():  St9bad_alloc
 
Thanks for reporting this. Actually it's a bug (or rather, several bugs)
in polynomial GCD. I'm working on a fix.

Best regards,
	Alexei

P.S.

> (Test case 9 in the attached publication)

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