Re: [Maxima-discuss] ratsimp not working as expected

[andre m. <and...@gm...>]

On 03/07/2014 03:52 AM, Richard Fateman wrote:
> On 3/6/2014 6:37 PM, andre maute wrote:
>> Hi list,
>>
>> here is my next one, consider the following test case,
>> which I wasn't able to reduce more.
>> If one comments the line marked trigger, the other ratsimp line chokes.
>>
>> Kind regards
>> Andre
>>
>> --- ratsimp-bug1.max -------------------------
>> display2d : false;
>> d : 4;
>> A : genmatrix(lambda([k,l],v[[k,l]]-v[[0,l]]),d,d);
>> detA : factor(determinant(A));
>> AinvT : transpose(invert(A));
>> /* AinvT : ratsimp(AinvT); /* error trigger */ */
>> zz : [0,-1,0,0];
>> h1 : transpose(matrix(zz));
>> h2 : AinvT.h1;
>> h3 : sum(h2[m,1]^2,m,1,d)*detA^2;
>> res : ratsimp(h3); /* chokes if trigger is commented */
>> --- ratsimp-bug1.max -------------------------
>>
>> --- ratsimp-bug1.txt -------------------------
>>
>> ... lots of text ...
>>
>> (%i11) res:ratsimp(h3)
>> Quotient by a polynomial of higher degree
>>    -- an error. To debug this try: debugmode(true);
>>
>> --- ratsimp-bug1.txt -------------------------
>
> It worked for me.
> (%o24) ?%build_info("5.30.0","2013-06-01 21:29:43","i686-pc-mingw32",
>                     "GNU Common Lisp (GCL)","GCL 2.6.8")
>
> note that
> gcd;
>   has value spmod.
>
> Sometimes changing that removes the mysterious bug .. Quotient ..etc.
> try gcd:subres  perhaps.
>

adding gcd:subres made it worse.
I let it run for 5 minutes (> 3Ghz machine)
and cancelled after it allocated over 9 gigabytes.
Did you use gcd:subres when it worked for you with GCL?

Andre