Optimization in Octave

[Urs Hackstein]

Dear all,

we have the following optimization problem: Given a (nonlinear, but
almost everywhere differentiable) function

p:[0.5,20]^4*[5,200]\to\mathbb{C}

we want to find the maximum of

Re(p(x_1,x_2,x_3,x_4,x_5))

for fixed imaginary part
Im(p(x_1,x_2,x_3,x_4,x_5))=y_0.
Is it possible to solve this problem using Octave?
Thanks a lot in advance!

Best regards,

Urs Hackstein