My Statement：

variable sigma(1,1) %%% sigma:对应 σ

variable eta(1,1)

constraint(1) = power(2,eta)-sigma;

My Constraints：

subject to

real(constraint)<=0;

During the iteration process, the first iteration runs normally without errors. But on the second iteration, the following error occurred:

The following error occurred when converting from cvx to double:

Cannot convert from cvx to double.

What’s the matter, please? Hope to get your answer, thank you