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Ground transport Description
Further explanation of this example: 'Applications of optimization with Xpress-MP', Chapter 10: Ground transport
Source Files
Data Files
e2minflow.mos (!****************************************************** Mosel Example Problems ====================== file e2minflow.mos `````````````````` Choosing the mode of transport (Minimum cost flow) (c) 2008 Fair Isaac Corporation author: S. Heipcke, Mar. 2002 *******************************************************!) model "E-2 Minimum cost flow" uses "mmxprs" declarations NODES: set of string ! Set of nodes MINQ : integer ! Total quantity to transport A: array(ARCS:range,1..2) of string ! Arcs COST: array(ARCS) of integer ! Transport cost on arcs MINCAP,MAXCAP: array(ARCS) of integer ! Minimum and maximum arc capacities end-declarations initializations from 'e2minflow.dat' A MINQ MINCAP MAXCAP COST end-initializations finalize(ARCS) ! Calculate the set of nodes NODES:=union(a in ARCS) {A(a,1),A(a,2)} declarations flow: array(ARCS) of mpvar ! Flow on arcs end-declarations ! Objective: total transport cost Cost:= sum(a in ARCS) COST(a)*flow(a) ! Flow balance: inflow equals outflow forall(n in NODES | n<>"SOURCE" and n<>"SINK") sum(a in ARCS | A(a,2)=n) flow(a) = sum(a in ARCS | A(a,1)=n) flow(a) ! Min and max flow capacities forall(a in ARCS | MAXCAP(a) > 0) do flow(a) >= MINCAP(a) flow(a) <= MAXCAP(a) end-do ! Minimum total quantity to transport sum(a in ARCS | A(a,1)="SOURCE" ) flow(a) >= MINQ ! Solve the problem minimize(Cost) ! Solution printing writeln("Total cost: ", getobjval) forall(a in ARCS) write( if(getsol(flow(a))>0, A(a,1) + " -> "+ A(a,2) + ": "+ getsol(flow(a))+"\n", "")) end-model | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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