While loop not terminating when condition is met?

% This is a part of my code where all these variables that aren't defined here have
% been previously defined. W0g is a constant value and R is varied which changes W0
R = 1;
while 1
   We_W0 = (a1+(b*W0g^C_1*AR^C_2*x_W0^C_3*W0_S^C_4*max^C_5))*Kvs
   if(type == 1)
       W3_W2 = exp((-R*SCF)/((V*(L_Dc))));
   else
       W3_W2 = exp(-(R*SCFpower)/((np*(L_Dc))));
   end
   Wf3 = W2_W1*W1_W0*W0g*(1-W3_W2);
   Wf4 = W3_W2*W2_W1*W1_W0*W0g*(1-W4_W3);
   Wf5 = W4_W3*W3_W2*W2_W1*W1_W0*W0g*(1-W5_W4);
   Wftot = Wf1+Wf2+Wf3+Wf4+Wf5;
   Wf = 1.06*Wftot;
   W0 = (Wc+Wp+Wpd+Wf)/(1-We_W0);
    if W0 == W0g                       
        disp('Required range is');
        disp(R);
        break;
        
    else R = R + 1;
    end
end

The problem I'm having is that this condition is met. When I output the variable W0 there is a point where it is equal to W0g. Why is the while loop not stopping when this condition is met?

Thanks

[per isakson]

Set

>> format hex

and check whether they are really equal

>> a=1
a =
   3ff0000000000000
>> b=1+eps
b =
   3ff0000000000001

[per isakson]

If you want help, ignoring comments is not a good tactic.

See Why is 0.3 - 0.2 - 0.1 (or similar) not equal to zero? and add this line above if W0 == W0g

fprintf( 1,'>>> %bx\n    %bx\n', W0, W0g );

[Nick Nuzzo]

Thank you per isakson. I just ended up breaking the loop when the value of the ratio of W0 and W0g was very close to 1.

Answer 1

[Walter Roberson]

The only time you should ever compare for floating point equality is a situation where one of the numbers has been extracted from an array , and the array members are being compared. For example it is okay to compare xx(kk) to min(xx) because min will return a bit for bit identical copy of a value from the array .

There are also some cases you can count on involving multiplication and division by 2 or 4. (xx/2)*2== xx will be true for floating point xx not nan and not between eps(realmin) and realmin

But otherwise never compare a calculated value for equality. (xx/3)*3 ==xx is not always true.