Hello there,

I was trying to solve an analytic center finding problem via modelling it in CVX. After compilation of the model, CVX returned an error message, saying that…

x = analytic_center(A,b)

CVX Warning:

Models involving “log” or other functions in the log, exp, and entropy

family are solved using an experimental successive approximation method.

The method requires multiple calls to the solver, so it can be slow; and

in certain cases it fails to converge. See Appendix D of the the user’s

guide for more information about this method, and for instructions on how

to suppress this warning in the future.

??? Undefined function or variable “tlX”.

Error in ==> cvxprob.solve at 314

tol = max( tlX );

Error in ==> cvx_end at 77

solve( prob );

Error in ==> analytic_center at 33

cvx_end

My model is

function [an_center, cvx_optval] = analytic_center(A,b)

n = size(A,2);

cvx_begin quiet

variable x(n);

maximize(sum(log(x)));

subject to

A*x==b;

x>=0;

cvx_end

an_center = x;

end

and I used random data to test the code:

A = randn(10,10);

b = randn(10,1);

I also have to mention that I use a startup.m file, which contains these lines:

addpath c:\users\user\documents\matlab’external libraries’\cvx

addpath c:\users\user\documents\matlab’external libraries’\cvx\structures

addpath c:\users\user\documents\matlab’external libraries’\cvx\lib

addpath c:\users\user\documents\matlab’external libraries’\cvx\functions

addpath c:\users\user\documents\matlab’external libraries’\cvx\commands

addpath c:\users\user\documents\matlab’external libraries’\cvx\builtins

addpath c:\users\user\documents\matlab’external libraries’\cvx\keywords

addpath c:\users\user\documents\matlab’external libraries’\cvx\sets

Problem didn’t solved by removing this file and rerunning cvx_setup.

I had used this code successfully years before, when I coded it as part of my BSc thesis. So, to get such an error by just running this code using the same CVX distribution installed to the same MATLAB version caught me by surprise. I’m pretty sure that I didn’t make any change in the CVX code (I don’t know how to upload solve.m here in order to have my claim verified). Please, suggest me a solution or workaround to this error.

I use CVX v. 1.22 in MATLAB 7.6, under Windows 8.1 x64.

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