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'producer_consumer' constraints: solving a resource-constrained project scheduling problem Description So-called 'producer_consumer' relations combine tasks that produce or consume quantities of the same non-renewable resource. Such problems may be modeled in two ways, namely
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producer_consumer_alt_graph.mos
(!****************************************************************
CP example problems
===================
file producer_consumer_graph.mos
````````````````````````````````
Resource-constrained project planning problem (construction of
a house) modeled with a producer-consumer constraint.
*** This model cannot be run with a Community Licence ***
(c) 2008 Artelys S.A. and Fair Isaac Corporation
Creation: 2007, rev. Sep. 2017
*****************************************************************!)
model "Cumulative Scheduling"
uses "kalis","mmsvg"
forward procedure draw_solution
setparam("KALIS_DEFAULT_LB",0)
setparam("KALIS_DEFAULT_UB",100)
declarations
! Task indices
Masonry = 1; Carpentry = 2; Roofing = 3; Windows = 4
Facade = 5; Garden = 6; Plumbing = 7; Ceiling = 8
Painting = 9; MovingIn = 10; InitialPayment = 11; SecondPayment = 12
BUILDTASKS = 1..10
PAYMENTS = 11..12
TASKS = BUILDTASKS+PAYMENTS
TNAMES: array(TASKS) of string
obj:cpvar ! Objective variable
starts : array(TASKS) of cpvar ! Start times of the tasks
ends : array(TASKS) of cpvar ! Completion times of the tasks
durations: array(TASKS) of cpvar ! Durations of the tasks
consos : dynamic array(TASKS) of cpvar ! Res. consumptions of the tasks
sizes : dynamic array(TASKS) of cpvar ! Consumption sizes (= conso x dur)
prods : dynamic array(TASKS) of cpvar ! Res. production of the tasks
sizep : dynamic array(TASKS) of cpvar ! Production sizes (= prod x dur)
Strategy : array(range) of cpbranching ! Branching strategy
end-declarations
TNAMES:: (1..12)["Masonry", "Carpentry", "Roofing", "Windows", "Facade",
"Garden", "Plumbing", "Ceiling", "Painting", "MovingIn",
"InitialPayment", "SecondPayment"]
! Setting the names of the variables
forall(j in TASKS) do
starts(j).name := TNAMES(j)+".start"
ends(j).name := TNAMES(j)+".end"
durations(j).name := TNAMES(j)+".duration"
end-do
! Creating consumption variables
forall(j in BUILDTASKS) do
create(sizes(j))
sizes(j).name := TNAMES(j)+".size"
create(consos(j))
consos(j).name := TNAMES(j)+".conso"
end-do
! Setting durations of building tasks
durations(Masonry) = 7; durations(Carpentry) = 3; durations(Roofing) = 1
durations(Windows) = 1; durations(Facade) = 2; durations(Garden) = 1
durations(Plumbing) = 8; durations(Ceiling) = 3; durations(Painting) = 2
durations(MovingIn) = 1
! Precedence constraints among building tasks
starts(Carpentry) >= ends(Masonry)
starts(Roofing) >= ends(Carpentry)
starts(Windows) >= ends(Roofing)
starts(Facade) >= ends(Roofing)
starts(Garden) >= ends(Roofing)
starts(Plumbing) >= ends(Masonry)
starts(Ceiling) >= ends(Masonry)
starts(Painting) >= ends(Ceiling)
starts(MovingIn) >= ends(Windows)
starts(MovingIn) >= ends(Facade)
starts(MovingIn) >= ends(Garden)
starts(MovingIn) >= ends(Painting)
! Setting task consumptions
consos(Masonry) = 7; consos(Carpentry) = 3; consos(Roofing) = 1
consos(Windows) = 1; consos(Facade) = 2; consos(Garden) = 1
consos(Plumbing) = 8; consos(Ceiling) = 3; consos(Painting) = 2
consos(MovingIn) = 1
! Production (amount) of payment tasks
forall(j in PAYMENTS) do
create(prods(j))
prods(j).name := TNAMES(j)+".prod"
create(sizep(j))
sizep(j).name := TNAMES(j)+".sizep"
end-do
! Payment data
prods(InitialPayment) = 20; prods(SecondPayment) = 9
durations(InitialPayment) = 1; durations(SecondPayment) = 1
starts(InitialPayment) = 0; starts(SecondPayment) = 15
! Objective: makespan of the schedule
obj = maximum({ ends(Masonry) , ends(Carpentry), ends(Roofing), ends(Windows), ends(Facade), ends(Garden), ends(Plumbing), ends(Ceiling), ends(Painting), ends(MovingIn)})
! Posting the producer_consumer constraint
producer_consumer(starts, ends, durations, prods, sizep, consos, sizes)
! Setting the search strategy
Strategy(0) := assign_var(KALIS_SMALLEST_MIN, KALIS_MIN_TO_MAX, starts)
cp_set_branching(Strategy)
! Find the optimal solution
if cp_minimize(obj) then
cp_show_sol
draw_solution
else
writeln("No solution found")
end-if
! Pretty display of the solution as an SVG user graph
procedure draw_solution
ind := 1
mkspan := 0
RES := 1
HORIZON := getub(obj)
forall(t in 0..HORIZON) histogram(RES,t) := 0
svgaddgroup("TextPlot", "", SVG_BLACK)
setrandseed(17)
forall(t in BUILDTASKS) do
svgaddgroup("G"+TNAMES(t), TNAMES(t), svgcolor(20+round(random*200),
20+round(random*200), 20+round(random*200)))
svgsetstyle(SVG_FILL,SVG_CURRENT)
svgsetstyle(SVG_OPACITY,0.65)
startt := getsol(starts(t))
endt := getsol(ends(t))
uset := getsol(consos(t))
if mkspan < endt then
mkspan := endt
end-if
svgaddrectangle(startt, ind, endt-startt, uset)
! svgaddtext(startt+1, ind-4, "t"+t)
forall(h in startt..HORIZON) histogram(RES,h) -= uset
ind += uset
end-do
forall(t in PAYMENTS) do
svgaddgroup("P"+TNAMES(t), TNAMES(t), SVG_BLUE)
svgsetstyle(SVG_FILL,SVG_CURRENT)
svgsetstyle(SVG_FILLOPACITY,0.5)
startt := getsol(starts(t))
endt := getsol(ends(t))
uset := getsol(prods(t))
if mkspan < endt then
mkspan := endt
end-if
svgaddrectangle(startt, (RES*-20), endt-startt, uset)
svgaddtext(startt,RES*-21,"Payment "+t)
forall (h in startt..HORIZON) histogram(RES,h) += uset
end-do
svgaddtext("TextPlot", mkspan, 0, "MakeSpan = " + mkspan)
svgaddgroup("Money", "Money available ", SVG_RED)
svgsetstyle(SVG_FILL,SVG_CURRENT)
svgsetstyle(SVG_FILLOPACITY,0.65)
svgaddpolygon(sum(h in 0..mkspan-1)[h, ((RES*-20)+histogram(RES,h)), h+1, ((RES*-20)+histogram(RES,h))]+[mkspan,RES*-20,0,RES*-20])
svgsetgraphscale(10)
svgsetgraphviewbox(0,-25*RES, mkspan+10, 25*RES+ind)
svgsetgraphlabels("Time","")
svgsave("prodcons.svg")
svgrefresh
svgwaitclose("Close browser window to terminate model execution.", 1)
end-procedure
end-model
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