title: Different scores when training XGBoost models in different machines
body: <p>On trying XGBoost's Demo on Ranking feature that it has: <a href="https://github.com/dmlc/xgboost/tree/master/demo/rank" rel="nofollow noreferrer">https://github.com/dmlc/xgboost/tree/master/demo/rank</a></p>
  
  <p>There different prediction scores that generated on different machines. Is that expected?</p>
  
  <p>I have run the same scripts on different machines:</p>
  
  <ol>
  <li>Local Macbook environment </li>
  <li>Amazon Linux in the remote environment), and the output that gets written to the file: <code>pred.txt</code> </li>
  </ol>
  
  <p>Sample output of the script in the <code>demo/rank</code> example:</p>
  
  <pre><code>bash-4.2# ./runexp.sh
  [01:13:08] 9630x47 matrix with 233775 entries loaded from mq2008.train
  [01:13:08] 471 groups are loaded from mq2008.train.group
  [01:13:08] 2707x47 matrix with 64764 entries loaded from mq2008.vali
  ....
  ....
  [01:13:08] 2874x47 matrix with 71241 entries loaded from mq2008.test
  [01:13:08] 156 groups are loaded from mq2008.test.group
  [01:13:08] start prediction...
  [01:13:08] writing prediction to pred.txt
  </code></pre>
  
  <p>The output in the Amazon Linux Machine</p>
  
  <pre><code>bash-4.2# head pred.txt
  0.78357064724
  0.16863465309
  0.71193027496
  0.68881440163
  </code></pre>
  
  <p>The output on MacBook</p>
  
  <pre><code>% head pred.txt
  0.72682631016
  0.15482419729
  0.65316188335
  0.67612731457
  </code></pre>
  
  <p>The same XGBoost code has been compiled on both machines (using <code>build.sh</code> in the root XGBoost folder).</p>