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From: andre m. <and...@gm...> - 2024-01-10 02:24:35
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I can confirm that a self-compiled maxima 5.47.0 doesn't have this sign problem. So for me this can be ignored. Regards Andre On 1/10/24 02:26, Richard Fateman wrote: > I get 2 for determinant_by_lu in Maxima 5.47.0 without loading anything. > > > On Tue, Jan 9, 2024 at 5:10 PM andre maute via Maxima-discuss < > max...@li...> wrote: > >> Hi list, >> >> this one from Michel Talon's post on the bird algorithm caught my >> attention. >> So I did some quick tests, mostly for checking that invert_by_lu, which I >> use a lot, is not affected. >> >> See the output below, my file is attached. >> One can see the matrices from the P.L.U decomposition don't have issues. >> But determinant_by_lu for the permutation matrix looks to be broken. >> >> Is this a known defect/bug? >> >> Regards Andre >> >> -------------------------- >> Maxima 5.45.1 https://maxima.sourceforge.io >> using Lisp SBCL 2.0.1-8.fc36 >> Distributed under the GNU Public License. See the file COPYING. >> Dedicated to the memory of William Schelter. >> The function bug_report() provides bug reporting information. >> (%i1) batch("detbylu.mac") >> >> read and interpret /home/user/detbylu.mac >> (%i2) display2d:false >> (%o2) false >> (%i3) A:matrix([1,0,-1,-1],[-1,0,1,-1],[0,0,-1,1],[1,-1,0,1]) >> (%o3) matrix([1,0,-1,-1],[-1,0,1,-1],[0,0,-1,1],[1,-1,0,1]) >> (%i4) determinant(A) >> (%o4) 2 >> (%i5) determinant_by_lu(A) >> (%o5) -2 >> (%i6) Ainv:invert_by_lu(A) >> (%o6) >> matrix([0,-1,-1,0],[-1/2,-3/2,-1,-1],[-1/2,-1/2,-1,0],[-1/2,-1/2,0,0]) >> (%i7) Ainv . A >> (%o7) matrix([1,0,0,0],[0,1,0,0],[0,0,1,0],[0,0,0,1]) >> (%i8) determinant(Ainv) >> (%o8) 1/2 >> (%i9) determinant_by_lu(Ainv) >> (%o9) -1/2 >> (%i10) [P,L,U]:get_lu_factors(lu_factor(A)) >> (%o10) >> [matrix([1,0,0,0],[0,0,0,1],[0,0,1,0],[0,1,0,0]),matrix([1,0,0,0],[1,1,0,0],[0,0,1,0],[-1,0,0,1]),matrix([1,0,-1,-1],[0,-1,1,2],[0,0,-1,1],[0,0,0,-2])] >> (%i11) M:P . L . U-A >> (%o11) matrix([0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0]) >> (%i12) P >> (%o12) matrix([1,0,0,0],[0,0,0,1],[0,0,1,0],[0,1,0,0]) >> (%i13) determinant(P) >> (%o13) -1 >> (%i14) determinant_by_lu(P) >> (%o14) 1 >> (%i15) L >> (%o15) matrix([1,0,0,0],[1,1,0,0],[0,0,1,0],[-1,0,0,1]) >> (%i16) determinant(L) >> (%o16) 1 >> (%i17) determinant_by_lu(L) >> (%o17) 1 >> (%i18) U >> (%o18) matrix([1,0,-1,-1],[0,-1,1,2],[0,0,-1,1],[0,0,0,-2]) >> (%i19) determinant(U) >> (%o19) -2 >> (%i20) determinant_by_lu(U) >> (%o20) -2 >> (%i21) B:matrix([1,0,0,0],[0,0,0,1],[0,0,1,0],[0,1,0,0]) >> (%o21) matrix([1,0,0,0],[0,0,0,1],[0,0,1,0],[0,1,0,0]) >> (%i22) determinant(B) >> (%o22) -1 >> (%i23) determinant_by_lu(B) >> (%o23) 1 >> (%o24) "/home/user/detbylu.mac" >> >> -------------------------------_______________________________________________ >> Maxima-discuss mailing list >> Max...@li... >> https://lists.sourceforge.net/lists/listinfo/maxima-discuss >> > |