Kautz graph




Example of Kautz graph on 3 characters with string length 2 (on the left) and 3 (on the right); the edges on the left correspond to the vertices on the right.


The Kautz graph KMN+1displaystyle K_M^N+1K_M^N+1 is a
directed graph of degree Mdisplaystyle MM and dimension N+1displaystyle N+1N+1, which has (M+1)MNdisplaystyle (M+1)M^N(M+1)M^N vertices labeled by all
possible strings s0⋯sNdisplaystyle s_0cdots s_Ns_0cdots s_N of length N+1displaystyle N+1N+1 which are composed of characters sidisplaystyle s_is_i chosen from
an alphabet Adisplaystyle AA containing M+1displaystyle M+1M+1 distinct
symbols, subject to the condition that adjacent characters in the
string cannot be equal (si≠si+1displaystyle s_ineq s_i+1s_ineq s_i+1).


The Kautz graph KMN+1displaystyle K_M^N+1K_M^N+1 has (M+1)MN+1displaystyle (M+1)M^N+1(M+1)M^N+1 edges


si∈Asi≠si+1displaystyle ;s_iin A;s_ineq s_i+1,;s_iin A;s_ineq s_i+1,


It is natural to label each such edge of KMN+1displaystyle K_M^N+1K_M^N+1
as s0s1⋯sN+1displaystyle s_0s_1cdots s_N+1s_0s_1cdots s_N+1, giving a one-to-one correspondence
between edges of the Kautz graph KMN+1displaystyle K_M^N+1K_M^N+1
and vertices of the Kautz graph
KMN+2displaystyle K_M^N+2K_M^N+2.


Kautz graphs are closely related to De Bruijn graphs.



Properties


  • For a fixed degree Mdisplaystyle MM and number of vertices V=(M+1)MNdisplaystyle V=(M+1)M^NV=(M+1)M^N, the Kautz graph has the smallest diameter of any possible directed graph with Vdisplaystyle VV vertices and degree Mdisplaystyle MM.

  • All Kautz graphs have Eulerian cycles. (An Eulerian cycle is one which visits each edge exactly once—This result follows because Kautz graphs have in-degree equal to out-degree for each node)

  • All Kautz graphs have a Hamiltonian cycle (This result follows from the correspondence described above between edges of the Kautz graph KMNdisplaystyle K_M^NK_M^N and vertices of the Kautz graph KMN+1displaystyle K_M^N+1K_M^N+1; a Hamiltonian cycle on KMN+1displaystyle K_M^N+1K_M^N+1 is given by an Eulerian cycle on KMNdisplaystyle K_M^NK_M^N)

  • A degree-kdisplaystyle kk Kautz graph has kdisplaystyle kk disjoint paths from any node xdisplaystyle xx to any other node ydisplaystyle yy.


In computing


The Kautz graph has been used as a network topology for connecting processors in high-performance computing[1] and fault-tolerant computing[2] applications: such a network is known as a Kautz network.



Notes




  1. ^ Darcy, Jeff (2007-12-31). "The Kautz Graph". Canned Platypus. External link in |publisher= (help).mw-parser-output cite.citationfont-style:inherit.mw-parser-output .citation qquotes:"""""""'""'".mw-parser-output .citation .cs1-lock-free abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-subscription abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registrationcolor:#555.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration spanborder-bottom:1px dotted;cursor:help.mw-parser-output .cs1-ws-icon abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center.mw-parser-output code.cs1-codecolor:inherit;background:inherit;border:inherit;padding:inherit.mw-parser-output .cs1-hidden-errordisplay:none;font-size:100%.mw-parser-output .cs1-visible-errorfont-size:100%.mw-parser-output .cs1-maintdisplay:none;color:#33aa33;margin-left:0.3em.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-formatfont-size:95%.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-leftpadding-left:0.2em.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-rightpadding-right:0.2em


  2. ^ Li, Dongsheng; Xicheng Lu; Jinshu Su (2004). "Graph-Theoretic Analysis of Kautz Topology and DHT Schemes". Network and Parallel Computing: IFIP International Conference. Wuhan, China: NPC. pp. 308–315. ISBN 3-540-23388-1. Retrieved 2008-03-05.



This article incorporates material from Kautz graph on PlanetMath, which is licensed under the Creative Commons Attribution/Share-Alike License.







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