@defgroup graph_isomorphism Graph Isomorphism

 @ingroup algs

 \brief Algorithms for testing (sub)graph isomorphism

 This group contains algorithms for finding isomorph copies of a

 given graph in another one, or simply check whether two graphs are isomorphic.

 The formal definition of subgraph isomorphism is as follows.

 We are given two graphs, \f$G_1=(V_1,E_1)\f$ and \f$G_2=(V_2,E_2)\f$. A

 function \f$f:V_1\longrightarrow V_2\f$ is called \e mapping or \e

 embedding if \f$f(u)\neq f(v)\f$ whenever \f$u\neq v\f$.

 The standard <em>Subgraph Isomorphism Problem (SIP)</em> looks for a

 mapping with the property that whenever \f$(u,v)\in E_1\f$, then

 \f$(f(u),f(v))\in E_2\f$.

 In case of <em>Induced Subgraph Isomorphism Problem (ISIP)</em> one

 also requires that if \f$(u,v)\not\in E_1\f$, then \f$(f(u),f(v))\not\in

 E_2\f$

 In addition, the graph nodes may be \e labeled, i.e. we are given two

 node labelings \f$l_1:V_1\longrightarrow L\f$ and \f$l_2:V_2\longrightarrow

 L\f$ and we require that \f$l_1(u)=l_2(f(u))\f$ holds for all nodes \f$u \in

 G\f$.

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