# Cannot perform the operation: {concave} ./ {convex}

Hello, this is my code, I have the following error, but I don’t know what to do, please help me thank you

Disciplined convex programming error:
Cannot perform the operation: {concave} ./ {convex}

wrong ./ (第 19 行)
z = times( x, y, ‘./’ );

wrong Untitled7 (第 39 行)
maximize(sum(Q_total) ./ sum_inv_P_total_times_T)

B = 10^6;
sigma_squared = -90;
sigma_squared = 10^(sigma_squared/10);
E_max = 100;
P_max = 20;
R_min = 0;
I = 3;
T = 1000;
T_0 = 0;
T_2 = T;
A = 1;
rho_0 = 1;
d_i = [1, 2, 3];
% Optimization with CVX
cvx_begin
variables P_total(T) % Variables to be optimized
expression Q_total(I)
variables inv_P_total(T) % New variable for the inverse of transmission power

``````% Compute the step size for Riemann sum approximation
delta_t = T / numel(T);

for i = 1:I
R_i = B * log(1 + (P_total .* (A * rho_0 * d_i(i)^-2) ./ sigma_squared)) / log(2);
Q_total(i) = sum(R_i) * delta_t;

% C3: Data rate constraints
R_i >= R_min;
end

% Compute the inverse of transmission power
inv_P_total = 1 *inv_pos(P_total);

% Sum of inv_P_total multiplied by T for the objective
sum_inv_P_total_times_T = sum(inv_P_total) .* T;

maximize(sum(Q_total) ./ sum_inv_P_total_times_T)

subject to

sum(P_total) * T <= E_max;

P_total <= P_max;
``````

cvx_end

I believe that other then some constant multiplicative factors, `1/sum_inv_P_total_times_T` is a harmonic mean, which is concave, and can be handled as shown in section 3,2,7 “Harmonic mean” of 3 Conic quadratic optimization — MOSEK Modeling Cookbook 3.3.0 .However, I have no reason to believe that the objective function, which multiplies that by `sum(Q_total)` is concave. So your first task is to prove that the objective function is concave. If not, CVX is not the right tool for the problem.