#2059 algsys -- variable order dependent

None
closed
nobody
5
2016-10-04
2010-08-24
No

(%i1) algsys([z-a=%i*b,z+a=c,a*z+3*(a-z)=13-12*%i,3*(z-a)+a*z=12*%i+13],[a,c,b,z]);
(%o1) []

(%i2) algsys([z-a=%i*b,z+a=c,a*z+3*(a-z)=13-12*%i,3*(z-a)+a*z=12*%i+13],[z,a,c,b]);
(%o2) [[z=2*%i-3,a=-2*%i-3,c=-6,b=4],[z=-(3*%i+11)/(%i-3),a=3-2*%i,c=6,b=4]]

Discussion

  • Dieter Kaiser

    Dieter Kaiser - 2010-08-25

    I think this is a known bug. See ID: 1944012 - solve() fails depending on equation order.
    Dieter Kaiser

     
  • Robert Dodier

    Robert Dodier - 2013-07-26
    • labels: --> Lisp Core - Solving equations
    • Description has changed:

    Diff:

    --- old
    +++ new
    @@ -1,4 +1,3 @@
    -
     \(%i1\) algsys\(\[z-a=%i\*b,z+a=c,a\*z+3\*\(a-z\)=13-12\*%i,3\*\(z-a\)+a\*z=12\*%i+13\],\[a,c,b,z\]\);
     \(%o1\) \[\]
    
    • Group: --> None
     
  • David Billinghurst

    • status: open --> closed
     
  • David Billinghurst

    Closing, as this particular example now works. Perhaps due to recent changes to algsys.

    (%i1) eqs:[z-a=%i*b,z+a=c,a*z+3*(a-z)=13-12*%i,3*(z-a)+a*z=12*%i+13];
    
    (%o1) [z-a = %i*b,z+a = c,a*z+3*(a-z) = 13-12*%i,3*(z-a)+a*z = 12*%i+13]
    (%i2) map(lambda([u],algsys(eqs,u)), listify(permutations([a,c,b,z])));
    
    (%o2) [[[a = (-2*%i)-3,b = 4,c = -6,z = 2*%i-3],
            [a = 3-2*%i,b = 4,c = 6,z = 2*%i+3]],
           [[a = (-2*%i)-3,b = 4,z = 2*%i-3,c = -6],
            [a = 3-2*%i,b = 4,z = 2*%i+3,c = 6]],
           [[a = (-2*%i)-3,c = -6,b = 4,z = 2*%i-3],
            [a = 3-2*%i,c = 6,b = 4,z = 2*%i+3]],
           [[a = (-2*%i)-3,c = -6,z = 2*%i-3,b = 4],
            [a = 3-2*%i,c = 6,z = 2*%i+3,b = 4]],
           [[a = (-2*%i)-3,z = 2*%i-3,b = 4,c = -6],
            [a = 3-2*%i,z = 2*%i+3,b = 4,c = 6]],
           [[a = (-2*%i)-3,z = 2*%i-3,c = -6,b = 4],
            [a = 3-2*%i,z = 2*%i+3,c = 6,b = 4]],
           [[b = 4,a = (-2*%i)-3,c = -6,z = 2*%i-3],
            [b = 4,a = 3-2*%i,c = 6,z = 2*%i+3]],
           [[b = 4,a = (-2*%i)-3,z = 2*%i-3,c = -6],
            [b = 4,a = 3-2*%i,z = 2*%i+3,c = 6]],
           [[b = 4,c = -6,a = (-2*%i)-3,z = 2*%i-3],
            [b = 4,c = 6,a = 3-2*%i,z = 2*%i+3]],
           [[b = 4,c = -6,z = 2*%i-3,a = (-2*%i)-3],
            [b = 4,c = 6,z = 2*%i+3,a = 3-2*%i]],
           [[b = 4,z = 2*%i-3,a = (-2*%i)-3,c = -6],
            [b = 4,z = 2*%i+3,a = 3-2*%i,c = 6]],
           [[b = 4,z = 2*%i-3,c = -6,a = (-2*%i)-3],
            [b = 4,z = 2*%i+3,c = 6,a = 3-2*%i]],
           [[c = -6,a = (-2*%i)-3,b = 4,z = 2*%i-3],
            [c = 6,a = 3-2*%i,b = 4,z = 2*%i+3]],
           [[c = -6,a = (-2*%i)-3,z = 2*%i-3,b = 4],
            [c = 6,a = 3-2*%i,z = 2*%i+3,b = 4]],
           [[c = -6,b = 4,a = (-2*%i)-3,z = 2*%i-3],
            [c = 6,b = 4,a = 3-2*%i,z = 2*%i+3]],
           [[c = -6,b = 4,z = 2*%i-3,a = (-2*%i)-3],
            [c = 6,b = 4,z = 2*%i+3,a = 3-2*%i]],
           [[c = -6,z = 2*%i-3,a = (-2*%i)-3,b = 4],
            [c = 6,z = 2*%i+3,a = 3-2*%i,b = 4]],
           [[c = -6,z = 2*%i-3,b = 4,a = (-2*%i)-3],
            [c = 6,z = 2*%i+3,b = 4,a = 3-2*%i]],
           [[z = 2*%i-3,a = (-2*%i)-3,b = 4,c = -6],
            [z = 2*%i+3,a = 3-2*%i,b = 4,c = 6]],
           [[z = 2*%i-3,a = (-2*%i)-3,c = -6,b = 4],
            [z = 2*%i+3,a = 3-2*%i,c = 6,b = 4]],
           [[z = 2*%i-3,b = 4,a = (-2*%i)-3,c = -6],
            [z = 2*%i+3,b = 4,a = 3-2*%i,c = 6]],
           [[z = 2*%i-3,b = 4,c = -6,a = (-2*%i)-3],
            [z = 2*%i+3,b = 4,c = 6,a = 3-2*%i]],
           [[z = 2*%i-3,c = -6,a = (-2*%i)-3,b = 4],
            [z = 2*%i+3,c = 6,a = 3-2*%i,b = 4]],
           [[z = 2*%i-3,c = -6,b = 4,a = (-2*%i)-3],
            [z = 2*%i+3,c = 6,b = 4,a = 3-2*%i]]]
    
     

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