Recent changes to 125: Egregious bug in Solve/Algsyshttps://sourceforge.net/p/maxima/bugs/125/Recent changes to 125: Egregious bug in Solve/AlgsysenFri, 08 May 2015 22:03:18 -0000#125 Egregious bug in Solve/Algsyshttps://sourceforge.net/p/maxima/bugs/125/?limit=25#7887<div class="markdown_content"><p>Well, I definitely spoke (and pushed) too soon there. Just realised that the patch avoids the lisp error by completely breaking the example. Aargh. Will look into this further over the next couple of days.</p></div>Rupert SwarbrickFri, 08 May 2015 22:03:18 -0000https://sourceforge.net9ecf1227c6c776117c634bda7621d2298c3dc859#125 Egregious bug in Solve/Algsyshttps://sourceforge.net/p/maxima/bugs/125/?limit=25#32c8<div class="markdown_content"><p>I've just pushed a patch (<a class="alink" href="/p/maxima/code/ci/c813e4162ce2514705e1b64a718c0a4751cceb54">[c813e4]</a>) that avoids us dying with algebraic set to true.</p></div>Rupert SwarbrickFri, 08 May 2015 21:43:32 -0000https://sourceforge.net36ccf0d03cf1c98d87c21d2177878aa48c08695a#125 Egregious bug in Solve/Algsyshttps://sourceforge.net/p/maxima/bugs/125/?limit=25#48ac<div class="markdown_content"><p>I think I've figured out why this dies with algebraic set to true. I don't have a fix yet, but I'm attaching an org file with a (long!) discussion that explains what's happened.</p>
<p>Short version: We call SUBRESULT on two polynomials in the variable <code>b</code>. Some of the coefficients happen to contain <code>sqrt(b^3-4)</code>. When squaring the coefficients as part of the PRS calculation, the hidden <code>b</code>'s escape and play havoc with the rest of the algorithm.</p></div>Rupert SwarbrickSun, 11 Jan 2015 20:21:26 -0000https://sourceforge.nete4b11fca597b6ce594da71fcc3c59c0d5bef8468Egregious bug in Solve/Algsyshttps://sourceforge.net/p/maxima/bugs/125/In a very simple case, Solve/Algsys \(a\) reports many
incorrect solutions and \(b\) misses all the parameterized
solutions.
\-- Define equations
eqs: \[a+b+c=0, a\*b\*c=1\]
\-- These seem pretty simple, don't they?
\-- Solve 2 equations for 3 unknowns \(normal algsys\)
sols: solve\(eqs,\[a,b,c\]\)
\-- Gives 12 solutions
\-- Substitute back the solutions
subst: map\(lambda\(\[sol\],subst\(sol,eqs\)\),sols\)
\-- Big mess
\-- Now evaluate them numerically to eyeball them
rectform\(subst\),numer
\-- Surprise\! Only 6 of the 12 are right.
And it is completely missing the parametric solution\(s\)\!\!\!
For example,
a= 2 / \( sqrt\( Q^4-4\*Q \) - Q^2 \)
b= \( sqrt\( Q^4-4\*Q \) - Q^2 \) / \(2\*Q\)
c= Q
Stavros MacrakisWed, 18 Sep 2002 14:52:33 -0000https://sourceforge.net4e806773335fb886918de6629d8cd5556d318c06