

# Decomposition






Every structure should divide the information that they store across processors, in order to do this two main approach are considered inside OpenFPM.



Every structure should divide the information that they store across processors, considering that in our context multiple distributed structures can interact with each other and dynamically change, our particular focus is in mapping structures into common domain and decomposition and distribution strategies over this domain. Once this domain is defined two main approach are considered inside OpenFPM.






* Model decomposition:



* Domain decomposition

...  ...  @@ 20,14 +20,17 @@ The Fixed decomposition just divide the domain as the user specified and assign 





The data driven decomposition instead consider the volume of the information the structure store and divide the volume equally them equally regardless of the communication.






### Model decomposition



### Domain definition






In general the concept of common domain is not defined in general, can go from different way to reindex the information so from multiindex concept to mapping the information into common spaces discrete or continuos, In the following we will consider structures that map over Ndimensional spaces because at the moment is our main but not only interest






### Model decomposition






In a distributedmemory setting, where data are scattered across



processors, two factors are important: equal division of work across



processors and reduction of the communication overhead.



A typical approach, is to formulate the problem as a



graphpartitioning problem: the physical domain is divided into subsubdomains (_Domain decomposition_)



graphpartitioning problem: the domain is divided into subsubdomains (_Domain decomposition_)



(vertices of the graph), each of them carrying a weight modelling the computational cost.



The communication pattern between subdomains is represented as links



between the subsubdomains (edges of the graph) with weights formalizing

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