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Π₯Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠΈ ΡΠ»ΠΎΠΆΠ½ΠΎΡΡΠΈ: ΠΊΠ»ΠΈΠΊΠΎΠ²ΠΎΠ΅ ΡΠΈΡΠ»ΠΎ Π³ΡΠ°ΡΠ° ΠΌΠ½ΠΎΠ³ΠΎΠ³ΡΠ°Π½Π½ΠΈΠΊΠ° ΠΈ ΡΠΈΡΠ»ΠΎ ΠΏΡΡΠΌΠΎΡΠ³ΠΎΠ»ΡΠ½ΠΎΠ³ΠΎ ΠΏΠΎΠΊΡΡΡΠΈΡ
In the 1980s V.A. Bondarenko found that the clique number of the graph of a polytope in many cases corresponds to the actual complexity of the optimization problem on the vertices of the polytope. For an explanation of this phenomenon he proposed the theory of direct type algorithms. This theory asserts that the clique number of the graph of a polytope is the lower bound of the complexity of the corresponding problem in the so-called class of direct type algorithms. Moreover, it was argued that this class is wide enough and includes many classical combinatorial algorithms. In this paper we present a few examples, designed to identify the limits of applicability of this theory. In particular, we describe a modification of algorithms that is quite frequently used in practice. This modification takes the algorithms out of the specified class, while the complexity is not changed. Another, much closer to reality combinatorial characteristic of complexity is the rectangle covering number of the facet-vertex incidence matrix, introduced into consideration by M. Yannakakis in 1988. We give an example of a polytope with a polynomial (with respect to the dimension of the polytope) value of this characteristic, while the corresponding optimization problem is NP-hard.Π 1980-Ρ
Π³Π³. Π.Π. ΠΠΎΠ½Π΄Π°ΡΠ΅Π½ΠΊΠΎ ΠΎΠ±Π½Π°ΡΡΠΆΠΈΠ», ΡΡΠΎ ΠΊΠ»ΠΈΠΊΠΎΠ²ΠΎΠ΅ ΡΠΈΡΠ»ΠΎ Π³ΡΠ°ΡΠ° ΠΌΠ½ΠΎΠ³ΠΎΠ³ΡΠ°Π½Π½ΠΈΠΊΠ° Π²ΠΎ ΠΌΠ½ΠΎΠ³ΠΈΡ
ΡΠ»ΡΡΠ°ΡΡ
ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΠ΅Ρ ΡΠ΅Π°Π»ΡΠ½ΠΎΠΉ ΡΠ»ΠΎΠΆΠ½ΠΎΡΡΠΈ Π·Π°Π΄Π°ΡΠΈ ΠΎΠΏΡΠΈΠΌΠΈΠ·Π°ΡΠΈΠΈ Π½Π° Π²Π΅ΡΡΠΈΠ½Π°Ρ
ΡΡΠΎΠ³ΠΎ ΠΌΠ½ΠΎΠ³ΠΎΠ³ΡΠ°Π½Π½ΠΈΠΊΠ°. ΠΠ»Ρ ΠΎΠ±ΡΡΡΠ½Π΅Π½ΠΈΡ ΡΡΠΎΠ³ΠΎ ΡΠ΅Π½ΠΎΠΌΠ΅Π½Π° Π±ΡΠ»Π° ΠΏΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½Π° ΡΠ΅ΠΎΡΠΈΡ Π°Π»Π³ΠΎΡΠΈΡΠΌΠΎΠ² ΠΏΡΡΠΌΠΎΠ³ΠΎ ΡΠΈΠΏΠ°, ΡΡΠ²Π΅ΡΠΆΠ΄Π°ΡΡΠ°Ρ, ΡΡΠΎ ΠΊΠ»ΠΈΠΊΠΎΠ²ΠΎΠ΅ ΡΠΈΡΠ»ΠΎ Π³ΡΠ°ΡΠ° ΠΌΠ½ΠΎΠ³ΠΎΠ³ΡΠ°Π½Π½ΠΈΠΊΠ° ΡΠ²Π»ΡΠ΅ΡΡΡ Π½ΠΈΠΆΠ½Π΅ΠΉ ΠΎΡΠ΅Π½ΠΊΠΎΠΉ ΡΠ»ΠΎΠΆΠ½ΠΎΡΡΠΈ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΡΡΠ΅ΠΉ Π·Π°Π΄Π°ΡΠΈ Π² ΡΠ°ΠΊ Π½Π°Π·ΡΠ²Π°Π΅ΠΌΠΎΠΌ ΠΊΠ»Π°ΡΡΠ΅ Π°Π»Π³ΠΎΡΠΈΡΠΌΠΎΠ² ΠΏΡΡΠΌΠΎΠ³ΠΎ ΡΠΈΠΏΠ°. ΠΠΎΠ»Π΅Π΅ ΡΠΎΠ³ΠΎ, ΡΡΠ²Π΅ΡΠΆΠ΄Π°Π»ΠΎΡΡ, ΡΡΠΎ ΡΡΠΎΡ ΠΊΠ»Π°ΡΡ ΡΠ²Π»ΡΠ΅ΡΡΡ Π΄ΠΎΡΡΠ°ΡΠΎΡΠ½ΠΎ ΡΠΈΡΠΎΠΊΠΈΠΌ, Π²ΠΊΠ»ΡΡΠ°ΡΡΠΈΠΌ Π² ΡΠ΅Π±Ρ ΠΌΠ½ΠΎΠ³ΠΈΠ΅ ΠΊΠ»Π°ΡΡΠΈΡΠ΅ΡΠΊΠΈΠ΅ ΠΊΠΎΠΌΠ±ΠΈΠ½Π°ΡΠΎΡΠ½ΡΠ΅ Π°Π»Π³ΠΎΡΠΈΡΠΌΡ. Π Π½Π°ΡΡΠΎΡΡΠ΅ΠΉ ΡΠ°Π±ΠΎΡΠ΅ ΠΏΡΠΈΠ²ΠΎΠ΄ΠΈΡΡΡ Π½Π΅ΡΠΊΠΎΠ»ΡΠΊΠΎ ΠΏΡΠΈΠΌΠ΅ΡΠΎΠ², ΠΏΡΠΈΠ·Π²Π°Π½Π½ΡΡ
ΠΎΠ±ΠΎΠ·Π½Π°ΡΠΈΡΡ Π³ΡΠ°Π½ΠΈΡΡ ΠΏΡΠΈΠΌΠ΅Π½ΠΈΠΌΠΎΡΡΠΈ ΡΡΠΎΠΉ ΡΠ΅ΠΎΡΠΈΠΈ. Π ΡΠ°ΡΡΠ½ΠΎΡΡΠΈ, ΠΎΠΏΠΈΡΠ°Π½Π° Π΄ΠΎΠ²ΠΎΠ»ΡΠ½ΠΎ ΡΠ°ΡΡΠΎ ΠΈΡΠΏΠΎΠ»ΡΠ·ΡΠ΅ΠΌΠ°Ρ Π½Π° ΠΏΡΠ°ΠΊΡΠΈΠΊΠ΅ ΠΌΠΎΠ΄ΠΈΡΠΈΠΊΠ°ΡΠΈΡ Π°Π»Π³ΠΎΡΠΈΡΠΌΠΎΠ², Π²ΡΠ²ΠΎΠ΄ΡΡΠ°Ρ ΠΈΡ
ΠΈΠ· ΡΠΊΠ°Π·Π°Π½Π½ΠΎΠ³ΠΎ ΠΊΠ»Π°ΡΡΠ° (ΠΏΠΎΡΡΠ΄ΠΎΠΊ ΡΡΡΠ΄ΠΎΠ΅ΠΌΠΊΠΎΡΡΠΈ ΠΏΡΠΈ ΡΡΠΎΠΌ Π½Π΅ ΠΌΠ΅Π½ΡΠ΅ΡΡΡ). ΠΡΡΠ³ΠΎΠΉ, Π·Π½Π°ΡΠΈΡΠ΅Π»ΡΠ½ΠΎ Π±ΠΎΠ»Π΅Π΅ Π±Π»ΠΈΠ·ΠΊΠΎΠΉ ΠΊ ΡΠ΅Π°Π»ΡΠ½ΠΎΡΡΠΈ, ΠΊΠΎΠΌΠ±ΠΈΠ½Π°ΡΠΎΡΠ½ΠΎΠΉ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠΎΠΉ ΡΠ»ΠΎΠΆΠ½ΠΎΡΡΠΈ ΡΠ²Π»ΡΠ΅ΡΡΡ ΡΠΈΡΠ»ΠΎ ΠΏΡΡΠΌΠΎΡΠ³ΠΎΠ»ΡΠ½ΠΎΠ³ΠΎ ΠΏΠΎΠΊΡΡΡΠΈΡ ΠΌΠ°ΡΡΠΈΡΡ ΠΈΠ½ΡΠΈΠ΄Π΅Π½ΡΠΈΠΉ ΡΠ°ΡΠ΅Ρ-Π²Π΅ΡΡΠΈΠ½, Π²Π²Π΅Π΄Π΅Π½Π½ΠΎΠ΅ Π² ΡΠ°ΡΡΠΌΠΎΡΡΠ΅Π½ΠΈΠ΅ Π. Π―Π½Π½Π°ΠΊΠ°ΠΊΠΈΡΠΎΠΌ Π² 1988 Π³. ΠΡ ΠΏΡΠΈΠ²ΠΎΠ΄ΠΈΠΌ ΠΏΡΠΈΠΌΠ΅Ρ ΠΌΠ½ΠΎΠ³ΠΎΠ³ΡΠ°Π½Π½ΠΈΠΊΠ° Ρ ΠΏΠΎΠ»ΠΈΠ½ΠΎΠΌΠΈΠ°Π»ΡΠ½ΡΠΌ (ΠΎΡΠ½ΠΎΡΠΈΡΠ΅Π»ΡΠ½ΠΎ ΡΠ°Π·ΠΌΠ΅ΡΠ½ΠΎΡΡΠΈ ΠΌΠ½ΠΎΠ³ΠΎΠ³ΡΠ°Π½Π½ΠΈΠΊΠ°) Π·Π½Π°ΡΠ΅Π½ΠΈΠ΅ΠΌ ΡΡΠΎΠΉ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠΈ, Π·Π°Π΄Π°ΡΠ° ΠΎΠΏΡΠΈΠΌΠΈΠ·Π°ΡΠΈΠΈ Π½Π° Π²Π΅ΡΡΠΈΠ½Π°Ρ
ΠΊΠΎΡΠΎΡΠΎΠ³ΠΎ NP-ΡΡΡΠ΄Π½Π°