title: Hyperopt: Define parameter which is dependent on other parameter
body: <p>I am using <code>python</code> package <code>hyperopt</code> and I have a parameter <code>a</code> which requires to be larger than parameter <code>b</code>.</p>
  
  <p>For example, I hope my parameter space is like</p>
  
  <pre><code>from hyperopt import hp
  
  space = {"b": hp.uniform(0, 0.5), "a": hp.uniform(b, 0.5)}
  </code></pre>
  
  <p>Which, requires <code>a</code> to be at least larger than <code>b</code>, how can I do that?</p>
  
  <p>Thanks in advance</p>