# Disciplined convex programming error: Cannot perform the operation: {real affine} .* {convex}

(Mark L. Stone) #21

I believe that is non-convex as written, Why isn't CVX accepting my model? READ THIS FIRST!

However, can you expionentiate to produce
`(1+(P(1)*hix)./(P(2)*hix)+Ni) >= 2^R_min`
then multiply through the denominator with all signs being what they need to be? I don;t knwo whether that will work out.

Successive convex approximation is used in my algorithm
(Neelu Gupta) #22

Thank you and sorry for inconvenience,
P(1,1) and P(2,1) are optimizing variables, i have done whatever you say but problem with R3 which is (R1+R2 ), now same error occured with R3, what should i do with? and one more problem while doing this, after optimizing P(2,1) is always zero when i considered R3 as R_min for checking, problem will solved or not…like this
P =

``````0.0034
0.0000
``````

value of K:0.017166
value of P(1):0.003387
value of P(2):0.000000
value of gnx:1.328718
value of Phi_ERn:23.262592
value of updated mu_n:0.023263
value of j:9.000000

(Mark L. Stone) #23

Have you shown that `R3 >= R1+R2` is convex or transformable into a convex constraint?

(Neelu Gupta) #24

i tried but it is always P(1,1) / P(2,1) form, they are not separating
(P(1,1)*hjx) >= (1+(P(1,1)*hix))*inv_pos((P(2,1)hix)+Ni)+(P(2,1)hjx)(inv_pos(Nj))((P(2,1)*hjx)+Nj);
like this

(Neelu Gupta) #25

If I fixed Rth as a constant value but one optimizing variable is always zero, what does it mean?, is it not considering the constraint or anything or does it mean it is considering only one variable by taking one variable right side

(Mark L. Stone) #26

I don;t even know what problem you are solving if not all constraints have been successfully entered into and accepted by CVX. Any constraint which is not accepted by CVX is “ignored” by CVX and not part of the problem which it provides to the solver.

(Neelu Gupta) #27

Firstly thanks a lot for your support,
Sir author is using successive convex approximation in which objective function is convex and objective function is transformed by updating value. I also provided you my algorithm in previous question, i have seen you have discussed this problem 3 years ago,’’ [A concave maximization problem with Disciplined convex programming error: {invalid} .* {real affine} or {negative constant} "
this is my objective function
maximize(Mn-mu_n*(1+exp(-an*(gnx(1,t)(P(1,1)+P(2,1))-bn))))
(Mn,an,bn are constant value, mu_n is nonnegative variable (10^-6) ,P(1,1) & P(2,1) are optimizing variable and gnx is array of 10 random value
Getting error,
Disciplined convex programming error:
Cannot perform the operation: {invalid} .
{log-convex}
In one program it runs easily but by changing some parameter it is showing like that, please help me, and only because of you i have an hope to solve problem.

(Mark L. Stone) #28

Read Illegal operation: {invalid} + {mixed real affine/constant} and see whther that gives you some things to look at and think about.