1. I don't believe there is a software algorithm bug.
2. Commercial macsyma gave up (illegal mem ref.) probably because
it ran out of stack or memory. (A "system" bug?)
3. Subres works better / faster much of the time.
4. spmod has its own regimes of bad performance, and I think
that there are a number of reports of bugs in it, typically
manifested by "polynomial quotient not exact" messages.
(What this means is someone computed p=gcd(r,s) and then
expected to produce a polynomial by exactly dividing r by p.
But it didn't divide.)
RJF
Viktor T. Toth wrote:
>I pretty much got used to switching gcd to spmod for large calculations.
>I've been meaning to ask, why does gcd default to subres (with all the bugs)
>instead of the apparently far more reliable spmod algorithm?
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>Viktor
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