title: scipy optimize minimize always exit with REL_REDUCTION_OF_F_
body: <p>I'm minimizing some log-likelihood using <code>'L-BFGS-B'</code> and I don't want the algorithm to stop when <code>REL_REDUCTION_OF_F_ &lt;= factr*epsmch</code> so I set <code>ftol=0</code>:  </p>
  
  <pre><code>min_log = scipy.optimize.minimize(fun=minus_log_lik, x0=proc_param,
                                    method='L-BFGS-B', bounds=tuple(bounds),
                                    options={'ftol':0,'gtol':1e-06} 
  </code></pre>
  
  <p>However I always get a result with</p>
  
  <blockquote>
    <p>message: 'CONVERGENCE: REL_REDUCTION_OF_F_&lt;=_FACTR*EPSMCH' </p>
  </blockquote>
  
  <p>Does anyone know why? I tried to set ftol negative but this gives an error.</p>