Abstract
The Khrapchenko method of finding a lower bound for the complexity of binary formulas is extended to formulas in \(k\)-ary bases. The resulting extension makes it possible to evaluate the complexity of linear Boolean functions and a majority function of \(n\) variables when realized by formulas in the basis of all \(k\)-ary monotone functions and negation as \(\Omega(n^{g(k)})\), where \(g (k)=1+\Theta(1/\ln k)\). For a linear function, the complexity bound in this form is unimprovable. For \(k=3\), the sharper lower bound \(\Omega(n^{1.53})\) is proved.
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Notes
Bases \(B_1\) and \(B_2\) are said to be equivalent if \(L_{B_1}(f)=\Theta(L_{B_2}(f))\) for all functions \(f\) expressed in them.
The bases \(B_1\) and \(B_2\) are said to be strictly equivalent if \(L_{B_1}(f)=L_{B_2} (f)\) for any function \(f\) represented in them.
The expression \(f\preceq g\) means \(f=O(g)\).
The maximum exists, because the set of suitable numbers \(\chi\) is bounded and closed.
Otherwise, we consider the subgraph \(G'\subset G\) for which \(s(G)\) is attained and its cover by the graphs \(G_1\cap G'\) and \(G_2\cap G'\). Then it follows from \(s(G_1\cap G')+s(G_2\cap G')\ge s(G')\) that \(s(G_1)+s(G_2)\ge s(G)\).
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Translated from Matematicheskie Zametki, 2021, Vol. 109, pp. 419-435 https://doi.org/10.4213/mzm12802.
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Sergeev, I.S. Formula Complexity of a Linear Function in a \(k\)-ary Basis. Math Notes 109, 445–458 (2021). https://doi.org/10.1134/S0001434621030123
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DOI: https://doi.org/10.1134/S0001434621030123