How to solve a large list of simultaneous equations [closed]

asked 2018-04-25 17:53:15 -0500

PatrickLewis gravatar image

I am trying to solve a particular problem, but my test solution for setting up the code isn't working. I have tried two ways - one, which just outputs the same equations, and the other, I'm unsure on how to solve this large list of equations which are unrealistic to type out.

First attempt

var('a b c d e f g h i')

This outputs $$\begin{pmatrix} ab+ac+bc & cd+ae+bf & cg+ah+bi \\ bd+ce+af & de+df+ef & fg+dh+ei \\ bg+ch+ai & eg+fh+di & gh+gi+hi \end{pmatrix}$$ I then make $L=X$, then type these equations element wise into the simultaneous equation solver;


The output:

 a*e + b*f == 1, d*e + d*f + e*f == 0, b*g + c*h + a*i == 1, c*g + a*h + b*i == 0, e*g + f*h + d*i == 0, f*g + d*h + e*i == 1, g*h + g*i + h*i == 0]

Second attempt;

for i in range(0,3):
    for j in range(0,3):

This gives me a list of the equations, I then try the solver again;


This just gives me an error:

(a, b, c, d, e, f, g, h, i)
Error in lines 13-13
Traceback (most recent call last):
  File "/cocalc/lib/python2.7/site-packages/smc_sagews/", line 1013, in execute
    exec compile(block+'\n', '', 'single') in namespace, locals
  File "", line 1, in <module>
  File "/ext/sage/sage-8.1/local/lib/python2.7/site-packages/sage/symbolic/", line 976, in solve
    raise TypeError("%s is not a valid variable." % repr(i))
TypeError: 2 is not a valid variable.

The hope is that I will be able to extend this to larger matrices, so autonomy is welcomed greatly. But I will happily take any advice given I'm at a completely lose end. It is worth noting that the solution to this problem; $$PXP^{\dagger}=X$ is the identity matrix. My understanding is that the first method cannot find a closed form? I have even tried specifying that a,b,c,d,e,f,g,h,i are all 0 or 1 and this has not helped. I believe my second method is more on the right track, however I cannot afford to manually type out the 9 non-linear equations that pop out from the matrix solver.

edit retag flag offensive reopen merge delete

Closed for the following reason duplicate question by tmonteil
close date 2018-04-26 04:42:55.452355


Which question is it a duplicate of?

jipilab gravatar imagejipilab ( 2018-05-02 08:09:19 -0500 )edit