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5.1.1 Decomposition Phase
In the decompositiun phase on the RSI6ûûû. the model is fodated into GAMS and al1
data of the model, such as objective cwficients, consnaint coefficients and nght hand sides etc..
are stored in a GAMS dictionary with the narnes of genenc constraints or variables and the
elements of their anached sets. Then. WSET (Waterloo Structure Exploiting Tool), which
adopted and modified the basic feature of SPI (Scnicture Passing interface) of the original SET
(Structure Exploiting Tool) (Fragniere et ai. [Zûûû]), ~ads al1 the data from the GAMS dicaonuy
using the GAMS i/0 Ltbrary (GAIS [1996]) and partitions the whole problem into subproblems
according to pre-defined rules in a file. cailed the SET file. provided by the user. These mles
employ a public domain Regex libnry [1992] with the notion of regular expression (or pattern
matcher). The pytitioned data of the subproblerns are sent to each computer over r local nework,
using PVM.
For s clex presentation of the decomposition phase, we will illustrate with the following
four-region energy planning mode! with 10 periods ("chrisjin4._@"' is use& In the GAMS mode1
description. the nmes of linking variables and linking constraints start with the capital letter "L"
and the names of nonlinking variables and nonlinking consnaints stm with the capital letten
'*X" in order to comtly identify linking elements and nonlinking elemenü in the later stage of
partition (These particular letteen are not required by our sofovare - WSET could recognize other
chvacter strings to distinguish linking from nonlinking entities). The solver is changed to our
pdlel decomposition solver. called WATPAR (WATerloo PARdlel) instead of CPLEX.