Static null move CPW engine 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 &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;
        }
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.