user23554: I have two questions about a code implementing a static null move. The questions are in the code.
The code is extracted from here: CPW engine search code
 if (depth < 3
            && !is_pv
            && !flagInCheck
            &&  abs(beta - 1) > -INF + 100) // 1. Why this condition?
        {
            int static_eval = eval(alpha, beta, 1);

            int eval_margin = 120 * depth; // 2. Why 120? What does it mean?
            if (static_eval - eval_margin >= beta)
                return static_eval - eval_margin;
        }


user9684: Just guessing without reading all of the code to understand completely.
1) The third condition to not preform a Null Move is zugswang.  Another hint is that INF is used to report a mate-in-x. 
2)  The purpose of a Null Move is to determine if we could do nothing and still be better so to cause an early cutoff.  I assume that they represent a pawn value as 100, so they want a slightly higher favorable eval before it causes a cutoff.  

23554: <p>I have two questions about a code implementing a static null move. The questions are in the code.</p>

<p>The code is extracted from here: <a href="https://github.com/nescitus/cpw-engine/blob/2054969ef201c23e44774fd667c2b6843f04eede/search.cpp#L280" rel="nofollow noreferrer">CPW engine search code</a></p>

<pre><code> if (depth &lt; 3
            &amp;&amp; !is_pv
            &amp;&amp; !flagInCheck
            &amp;&amp;  abs(beta - 1) &gt; -INF + 100) // 1. Why this condition?
        {
            int static_eval = eval(alpha, beta, 1);

            int eval_margin = 120 * depth; // 2. Why 120? What does it mean?
            if (static_eval - eval_margin &gt;= beta)
                return static_eval - eval_margin;
        }
</code></pre>
 9684: <p>Just guessing without reading all of the code to understand completely.</p>

<p>1) The third condition to not preform a Null Move is zugswang.  Another hint is that INF is used to report a mate-in-x. </p>

<p>2)  The purpose of a Null Move is to determine if we could do nothing and still be better so to cause an early cutoff.  I assume that they represent a pawn value as 100, so they want a slightly higher favorable eval before it causes a cutoff.  </p>
