printing objective sum of squares error

[ddudt]

ObjectiveFunction.print_value does not always print the true sum of squares error.

Minimal working example:

from desc.equilibrium import Equilibrium
from desc.objectives import ObjectiveFunction, AspectRatio

eq = Equilibrium(L=2, M=2, N=0)
obj = ObjectiveFunction(AspectRatio(eq, target=7))
eq.solve(objective=obj, verbose=3)

Gives the output:

Starting optimization
Using method: lsq-exact
   Iteration     Total nfev        Cost      Cost reduction    Step norm     Optimality   
       0              1          4.500e+00                                    5.294e-15   
`gtol` condition satisfied.
         Current function value: 4.500e+00
         Total delta_x: 0.000e+00
         Iterations: 0
         Function evaluations: 1
         Jacobian evaluations: 1
Timer: Solution time = 210 ms
Timer: Avg time per step = 210 ms
Start of solver
Total (sum of squares):  5.000e+01, 
Aspect ratio:  3.000e+00 (dimensionless)
Aspect ratio:  3.000e+00 (normalized)

The initial aspect ratio is 10 and the target value is 7, so the error is 3. The corresponds to the cost of 1/2 * 3**2 = 4.5.
But the printed sum of squares is 1/2 * 10**2 = 50.

We should edit the print_value function so it gives the same sum of squares value as the optimizer displays.