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Nonlinear Equation Solve

From: Thomas D. Dean
Subject: Nonlinear Equation Solve
Date: Tue, 14 Feb 2012 12:22:22 -0800
User-agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120126 Thunderbird/9.0

I have a set of 15 nonlinear equations in 15 unknowns.
The equations are large, 3000 characters per equation, maybe 100 terms and of the form a1*(x1*x2*...*x14) + b1*(x1*x2* + ... + *x13*x15) + ...

The equations were generated by NEC4 and Maple for modeling an antenna.

The function eqnsetf is 55 lines, 144000 characters. The top of the function extracts the values of y into the proper values. eqnsetf(y) returns a reasonable looking vector.

I tried

> size(y)
  1 15
> [x, fval, info] =
   fsolve (@eqnsetf,y',optimset("TolX",1e-20,"TolFun",1e-20));
> info
info = 0

If I reduce the tol's, fsolve does not reach a solution.

> [x, fval, info] =
    fminunc (@eqnsetf,y',
error: __doglegm__: operator \: nonconformant arguments (op1 is 15x15, op2 is 225x1)
error: called from:
error: /usr/local/share/octave/3.4.3/m/optimization/fminunc.m at line 386, column 3 error: /usr/local/share/octave/3.4.3/m/optimization/fminunc.m at line 233, column 9

Any ideas?

Tom Dean

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