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Using 'exists' for loops over sparse arrays Description The models loop.mos/looph.mos and proj.mos show the effect of using the
keyword exists in conditions on loops over sparse arrays. As can be seen, the careful formulation of loops may result in a considerable speedup of the model execution time. Mosel defines two forms of sparse arrays, namely dynamic arrays and hashmap arrays. The model sparsearrays.mos compares the performance of these two forms for different cases of enumerations. Further explanation of this example:
'Mosel User Guide', Appendix 'Good modeling practice' explains in detail the correct use of exists.
Source Files Data Files proj.mos (!******************************************************* Mosel Example Problems ====================== file proj.mos ````````````` Show which indices are enumerated when looping over a sparse array (c) 2008 Fair Isaac Corporation author: S. Heipcke, 2001, rev. 2017 *******************************************************!) model "Show indices" declarations R1,R2,R3: range D: dynamic array(R1,R2,R3) of integer end-declarations initializations from 'proj1.dat' D end-initializations writeln("Standard enumeration of 'D':") forall(i in R1,j in R2,k in R3) writeln(i, " ", j, " ", k, ": ", D(i,j,k)) writeln("Enumeration of 'D' using 'exists':") forall(i in R1,j in R2,k in R3 | exists(D(i,j,k))) writeln(i, " ", j, " ", k, ": ", D(i,j,k)) ! Declare and initialize the same set, this time indexed by 'set of integer' declarations S1,S2,S3: set of integer C: dynamic array(S1,S2,S3) of integer end-declarations initializations from 'proj1.dat' C as 'D' end-initializations writeln("Standard enumeration of 'C':") forall(i in S1,j in S2,k in S3) writeln(i, " ", j, " ", k, ": ", C(i,j,k)) writeln("Enumeration of 'C' using 'exists':") forall(i in S1,j in S2,k in S3 | exists(C(i,j,k))) writeln(i, " ", j, " ", k, ": ", C(i,j,k)) end-model | |||||||||

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