improve conversion from algebraic to differential equations

mkauers / ore_algebra

GNU General Public License v2.0

29 stars 18 forks source link

improve conversion from algebraic to differential equations #52

Open mezzarobba opened 2 years ago

mezzarobba commented 2 years ago

Currently computing a differential operator annihilating an algebraic function can be done with (x*Dx).annihilator_of_composition(...). However this

is not easily discoverable,
is quite slow (compared to gfun),
tends to return non-minimal annihilators.

mkauers commented 2 years ago

Do you have an example for non-minimal output at hand? I think this should not happen.

mezzarobba commented 2 years ago

I couldn't find the full example, sorry. What I found is a quick note from May 2019 claiming that it happened with "the" generating function of Kreweras walks. However, I just tried again with the equation -64t^2K^3 - 16tK^2 + (72t - 1)K - 54*t + 1 and it works fine. I guess I made a mistake back then, or perhaps I used some variant of the generating function. (With the full generating function, the computation does not finish within a few minutes, so I guess it was not that...)