title: How does "line search failed" affect the optimization?
body: <p>I am using <code>scipy.optimize.minimize</code> for my optimization problem. Specifically, I tried solvers "L-BFGS-B" and "TNC", but both give me "Linear search failed"-like messages on my problem. What is the reason of the failure of the line search on these solvers? Does it mean that the final "optimal" value is potentially not optimal?</p>