Page 477 - ExtendSim User Guide

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Advanced Topics 451
LP technology
• Each decision variable in the objective function is the effective rate of a section in the LP area. For instance, the objective could be “Maximum effective rate = 1*ER1+ 1*ER2 + 1*ER3...”, where ERn is the effective rate for a rate section in the LP area.
• If there is no bias, or all the intermediate calculations related to bias order have been completed, the coefficient of each variable will be 1. If there is bias, the coefficient could be other than 1.
7) TheExecutivecommunicateswiththeLPSolver.
• TheExecutivegivestheLPSolvertheobjectivefunctionandtheinformationfromthe blocks and rate sections within the LP area.
• Critical constraints put an upper bound on some of the effective rates (the decision variables). Relational constraints provide a link between the effective rates of different rate sections and must be taken into consideration during the calculation. For instance, if effective rate X is less than or equal to effective rate Y, the objective function must conform to that information.
8) TheSolverperformsacalculation.
• TheSolvercalculatesanoptimizedsetofeffectiveratesfortheLParea.
• TheresultisanintermediateLPcalculation(ifthereisbias)orthefinalLPcalculation (if there is no bias).
• Forfulldetails,see“TheLPcalculation”onpage454. 9) Steps6-8arerepeated,ifnecessary.
• IftheblocksintheLPareahavebias,theExecutivemustdetermineintermediate objective functions and the Solver must perform intermediate calculations. The number of recalculations is equal to the number of blocks with bias, plus 1.
• For each recalculation, the list of critical and relational constraints is changed to include the constraints caused by the particular bias order being considered.
• See “Bias information” on page 452. 10)The rate sections are notified.
• The Executive sends “Executive block flow” messages to the head of the rate sections to update to the new effective rates.
• The blocks receiving this information update according to their dialogs and value con- nectors. They then post new events if necessary.
☞ Since the purpose of the recalculation is to maximize the entire set of effective rates, some rates will change while others might not.
Types of information provided to the Executive
When effective rates need to be recalculated, Rate library blocks provide critical and relational constraint and bias information to the Executive.
To learn which blocks contribute which types of information, see “Table summarizing con- straint and bias information” on page 453.
Flow rules
Flow rules consist of critical and relational constraints.
Discrete Rate
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