Unexpected result calculating the determinant of a singular matrix (42S)

[Claudio L.]

(10-21-2019 03:06 PM)Thomas Okken Wrote:  But the 48G returns exactly zero regardless of whether flag -54 is set or clear...

(Free42 Binary does not return zero, so the fact that Free42 Decimal does is apparently just a coincidence, not the result of a better algorithm. There is no "tiny element is zero" cheat in play either way.)

(The HP-15C returns 2e-9 (or rather, "15C Scientific Calculator by Vicinno," on iOS, but that should be the same thing).)

May or may not be a coincidence. There are division-free decomposition algorithms that preserve integers, so if an integer matrix is given, all operations remain integer up until the end. I don't know if this is the case for Free42 or the 48g, I know it is the case with newRPL.
My point is, you don't necessarily need a cheat to get a good result with integer matrices.

Here's one algorithm, for example (not the one I used, but same idea).

I think this one is the one used by newRPL.