Reducible (control) flow graph

Reducible (control) flow graph --- сводимый управляющий граф.

Let [math]\displaystyle{ G }[/math] be a cf-graph and let [math]\displaystyle{ k\geq 0 }[/math]. The [math]\displaystyle{ k }[/math]derived cf-graph [math]\displaystyle{ G_k }[/math] of [math]\displaystyle{ G }[/math], denoted [math]\displaystyle{ G_k=I_k(G) }[/math], is defined by the following rules: [math]\displaystyle{ G_0=G }[/math], and for any [math]\displaystyle{ k\gt 0 }[/math] the cf-graph [math]\displaystyle{ G_k }[/math] is derived from the cf-graph [math]\displaystyle{ G_{k-1} }[/math] by reduction of its maximal interval into nodes. The limit cf-graph of [math]\displaystyle{ G }[/math] is defined as its [math]\displaystyle{ k }[/math]-derived cf-graph [math]\displaystyle{ G_k }[/math] such that [math]\displaystyle{ G_k=I_{k+1}(G) }[/math]. [math]\displaystyle{ G }[/math] is called (interval) reducible if its limit cf-graph is trivial and (interval) irreducible otherwise.