Hello,

I am trying to solve a minimization problem. I have the ratio of two posynomials which I know from theory that it is non-convex problem .

So, in order two solve it I am doing some transfrmations on the denominator and finally I have a ratio of a posynomial and a monomial, which I also know that the result is a posynomial and it is in th standard form of geometric programming problem and it can be easily solved using interior point method.

my cvx code is as follows:

`cvx_begin gp quiet cvx_solver sedumi variables P_s P_r P_j minimize ( (P_s*b(5) + P_r*b(6) + P_r*P_j*b(7) )/ ( ((P_s*b(1))/a(1))^a(1) * ((P_s*P_j*b(2))/a(2))^a(2) * ((P_r*b(3))/a(3))^a(3) * ((P_r*P_j*b(4))/a(4))^a(4)) ) subject to P_tot^-1 *P_s + P_tot^-1 *P_r + P_tot^-1 *P_j <= 1; P_r*P_s^-1 * (a_r / deco_const) <= 1 ; cvx_end`

where a and b are vector with real values and a_r and deco_const also are real numbers. I followed all the rules for writing correct geometric programs.

The code is working most of the times, BUT sometimes,while I am doing many Monte Carlo simulations, this error is coming up:

**Error using +**

**Disciplined convex programming error:**

**Illegal operation:{log-affine} + {concave}**

I hope you can understand, if not I can give you more details.

Thank you in advance.