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Student Support Forum: 'Solving linear equations takes forever(??)' topicStudent Support Forum > General > "Solving linear equations takes forever(??)"

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Fabian Werner
12/01/11 08:53am

Hi.

I am trying to solve a homogeneous system of linear equations over the complex numbers. The matrix has approx. 250 rows and 54 columns so i assumed that this would take a few seconds to solve. Instead, when i try to run the program it just does not give me anything. I found out that i can compute the rank and the row reduced form if a certain constant remains unspecified (in my case it is cD = I / Sqrt[3]). When i set it i cannot compute anything, every command i try results in a seemingly endless loop.

I am not sure about the concrete description of my computer, it is possibly a slow one but fast enougth to run kde and so forth...
I am using Mathematica 8.0.1.0 on some Linux system.

The system of equations can be found here:
http://happy-werner.de/eqSet.txt

The source that i try to use is here:
http://happy-werner.de/weil_N_3_q_5.txt

The essential lines are as follows:

(* THIS DOES NOT WORK *)
(*
{b,m} = CoefficientArrays[eqSet, listOfAllAVars];
Print[LinearSolve[m, b]];
*)

(* THIS DOES WORK, BUT ONLY IS cD IS UNSET! *)
(*cD = I / Sqrt[3];*)
cfsComplete = Normal[CoefficientArrays[eqSet, listOfAllAVars]];
cfs = cfsComplete[[2]];
cfsNew = RowReduce[cfs];
Print[cfsNew];
Print[MatrixRank[cfsNew]];

Can anyone tell me what i am doing wrong?


Best wishes and thanks in advance,

Fabian Werner,
TU Darmstadt,
Germany



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