How can I deal with error:log({convex})?

1

Part of My code is as follow
Temp1 = log(1 + a / (b + c)) * 1.4427 - log(1 + a / (d(n,1) + c)) * 1.4427;
where a and c are constant, d is a variable and b is affine

When I run my code, this error appeared:
Disciplined convex programming error:
Cannot perform the operation: {positive constant} ./ {real affine}

I try to add inv_pos() to my code to deal with this error, then modify my code as
Temp1 = log(1 + a * inv_pos(b + c)) * 1.4427 - log(1 + a * inv_pos(d(n,1) + c)) * 1.4427;
Then the other error appeared:
Disciplined convex programming error:
Illegal operation: log( {convex} ).

These errors bothered me for a long time and make me feel headache. Could you please tell me how should I deal with them?

2

I think you will need to combine log(x) - log(y) into log(x/y) and see whether you can reformulate the x/y into a concave expression, possibly affine - inv_pos(concave) . For instance, something such as Can CVX solve this kind of function {x-log(1+0.01*x/(x+1))} . I don’t know whether that is possible, or indeed whether your original expression is convex or concave - if neither, it can’t be used in CVX.