<div dir="ltr"><div>After looking into the code, I noticed these in 'mc_ensembles.F' between lines 700-708:</div><div><br></div><div><div class="prettyprint" style="background-color: rgb(250, 250, 250); border-color: rgb(187, 187, 187); border-style: solid; border-width: 1px; word-wrap: break-word;"><code class="prettyprint"><div class="subprettyprint"><span style="color: #000;" class="styled-by-prettify">                  IF </span><span style="color: #660;" class="styled-by-prettify">(</span><span style="color: #000;" class="styled-by-prettify">nboxes </span><span style="color: #660;" class="styled-by-prettify">.</span><span style="color: #000;" class="styled-by-prettify">EQ</span><span style="color: #660;" class="styled-by-prettify">.</span><span style="color: #000;" class="styled-by-prettify"> </span><span style="color: #066;" class="styled-by-prettify">2</span><span style="color: #660;" class="styled-by-prettify">)</span><span style="color: #000;" class="styled-by-prettify"> THEN<br>                     IF </span><span style="color: #660;" class="styled-by-prettify">(</span><span style="color: #000;" class="styled-by-prettify">rand </span><span style="color: #660;" class="styled-by-prettify">.</span><span style="color: #000;" class="styled-by-prettify">LT</span><span style="color: #660;" class="styled-by-prettify">.</span><span style="color: #000;" class="styled-by-prettify"> </span><span style="color: #066;" class="styled-by-prettify">0.75E0</span><span style="color: #000;" class="styled-by-prettify">_dp</span><span style="color: #660;" class="styled-by-prettify">)</span><span style="color: #000;" class="styled-by-prettify"> THEN<br>                        box_number </span><span style="color: #660;" class="styled-by-prettify">=</span><span style="color: #000;" class="styled-by-prettify"> </span><span style="color: #066;" class="styled-by-prettify">1</span><span style="color: #000;" class="styled-by-prettify"><br>                     ELSE<br>                        box_number </span><span style="color: #660;" class="styled-by-prettify">=</span><span style="color: #000;" class="styled-by-prettify"> </span><span style="color: #066;" class="styled-by-prettify">2</span><span style="color: #000;" class="styled-by-prettify"><br>                     ENDIF<br>                  ELSE<br>                     box_number </span><span style="color: #660;" class="styled-by-prettify">=</span><span style="color: #000;" class="styled-by-prettify"> </span><span style="color: #066;" class="styled-by-prettify">1</span><span style="color: #000;" class="styled-by-prettify"><br>                  ENDIF</span></div></code></div><div><br></div></div><div><br></div><div>It looks like the pmtraion move is indeed 75% biased toward the first box.</div></div>