[R] Problems with constrOptim

[cianders at uci.edu]

I am having problems with the constrOptim problem. I am trying to compute
a function which must be concave. When I put the linear constraints in,
constrOptim always returns the original values of the parameter entered
after several iterations. However, if I set ui to the 0 matrix, it will
optimize the function. Does this imply the constraints are restraining the
algorithm from exploring the parameter space correctly?