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gams:model_a_band_matrix [2008/09/25 14:56]
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gams:model_a_band_matrix [2020/05/18 17:33] (current)
Lutz Westermann
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-A [[http://​en.wikipedia.org/​wiki/​Band_matrix|band matrix]] can be modeled efficiently in  GAMS using circular leads (''​++''​) and circular lags (''​%%--%%''​). See chapter ​13.of the GAMS User's Guide for more information. Using circular leads and lags, the first and last members of the set are assumed to be adjacent, so as to form a circular sequence of members. These operators only work with ordered sets.+A [[http://​en.wikipedia.org/​wiki/​Band_matrix|band matrix]] can be modeled efficiently in  GAMS using circular leads (''​++''​) and circular lags (''​%%--%%''​), see chapter ​[[https://​www.gams.com/​latest/​docs/​UG_OrderedSets.html#​UG_OrderedSets_LagLeadOperators|lag and lead operator]] ​of the GAMS User's Guide for more information. Using circular leads and lags, the first and last members of the set are assumed to be adjacent, so as to form a circular sequence of members. These operators only work with ordered sets.
  
-Find below  an example, where the usage of circular leads (equation ''​eq''​) was ~60 times faster than the original formulation using ''​sum''​ - statements and lots of comparisons (equation ''​eq1''​ and ''​eq2''​). Both models are identical.+Find below  an example, where the generation of a model with the usage of circular leads (equation ''​eq''​) was ~50 times faster than the original formulation using ''​sum''​ - statements and lots of comparisons (equation ''​eq1''​ and ''​eq2''​). Both models are identical.
  
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