MATLAB: I am trying to solve seven non linear equation with seven variables with fsolve comond but it show the error Solver stopped prematurely. fsolve stopped because it exceeded the function evaluation limit, options.MaxFunEvals = 700 (the default value).

fsolveoptions.maxfunevals

my problem is
function F=equ(z)
T(1)=z(1);
T(2)=z(2);
T(3)=z(3);
T(4)=z(4);
T(5)=z(5);
T(6)=z(6);
T(7)=z(7);
T(8)=30;
F(1)=(8851882195710375*T(1))/17592186044416 - 132778232935655625/8796093022208;
F(2)=(706377819630075746427*T(1))/879609302220800000 - 300*T(2) - 542714824148265632667/35184372088832000;
F(3)=(77119428673638711*(T(3))^4)/1662273001970115115220992 + 300*T(1) - 300*T(2) - (77119428673638711*(T(2))^4)/1662273001970115115220992;
F(4)=(77119428673638711*(T(2))^4)/1662273001970115115220992 - (2769*T(3))/20 + 300*T(4) - (3231*T(8))/20 - (77119428673638711*(T(3))^4)/1662273001970115115220992;
F(5)=(1619508002146412931*(T(4))^4)/166227300197011511522099200 + (3231*T(3))/20 - (4911*T(5))/20 + (3231*T(6))/20 - (1551*T(8))/20 - (1619508002146412931*(T(6))^4)/166227300197011511522099200 + 3276/25;
F(6)=(6092434865217458169*(T(4))^4)/166227300197011511522099200 + (3231*T(5))/20 - (9231*T(6))/20 + 300*T(7) - (6092434865217458169*(T(6))^4)/166227300197011511522099200;
F(7)=(7711942867363871*(T(7))^4)/151115727451828646838272 + (619*T(7))/2 - 300*T(6) - 2692139312343358067776095/9444732965739290427392;
end
please provide solution how to solve this

Best Answer

  • MaxFunEvals is an upper limit on the number of function evaluations that FSOLVE is allowed to use in its iterations. You can increase it using either optimset() or optimoptions(), and FSOLVE will iterate further to try to find a solution if you do.
    However, it can be shown analytically that your equations have no solution. Note that the first 2 equations can be used to solve for T(1) and T(2) directly. The result is T(1)=30 and T(2)=28.8896. Substituting these into the 3rd equation reduces it to
    4.6394e-08*T(3)^4 + 333.0926 =0
    The left hand side is a strictly positive expression for all T(3) and cannot be made zero.