(!****************************************************** Mosel Example Problems ====================== file j4grit.mos ``````````````` Gritting roads in a village (c) 2008 Fair Isaac Corporation author: S. Heipcke, Mar. 2002 *******************************************************!) model "J-4 Gritting circuit" uses "mmxprs" forward function find_unused(J: array(range) of integer):integer forward function add_path(node:integer, J: array(range) of integer):integer declarations ISEC = 1..12 ! Set of street intersections LEN: dynamic array(ISEC,ISEC) of integer ! Length of streets use: dynamic array(ISEC,ISEC) of mpvar ! Frequency of use of streets end-declarations initializations from 'j4grit.dat' LEN end-initializations forall(i,j in ISEC | exists(LEN(i,j))) create(use(i,j)) ! Objective: length of circuit Length:= sum(i,j in ISEC | exists(LEN(i,j))) LEN(i,j)*use(i,j) ! Balance traffic flow through intersections forall(i in ISEC) sum(j in ISEC) use(i,j) = sum(j in ISEC) use(j,i) ! Grit every street forall(i,j in ISEC | exists(LEN(i,j))) use(i,j) >= 1 ! Solve the problem minimize(Length) ! Solution printing writeln("Total length: ", getobjval) ct:=round(getsol(sum(i,j in ISEC) use(i,j))) declarations TOUR: array(1..ct+1) of integer TCOUNT: array(ISEC,ISEC) of integer end-declarations ! Main loop of the Eulerian circuit algorithm forall(i,j in ISEC | exists(LEN(i,j))) TCOUNT(i,j):=round(getsol(use(i,j))) TOUR(1):=1 ct-=add_path(1,TOUR) while(ct>0) ct-=add_path(find_unused(TOUR),TOUR) writeln("Tour: ", TOUR) !----------------------------------------------------------------- ! Find first node in list with free path(s) function find_unused(J: array(range) of integer):integer i:=1 returned:=1 while(J(i)>0 and i<getsize(J)) if in> 0) then returned:=J(i) break else i+=1 end-if end-function !----------------------------------------------------------------- ! Add a subtour to the current tour function add_path(node:integer, J: array(range) of integer):integer declarations NEWJ: array(1..getsize(J)) of integer end-declarations ! Insertion position pos:=1 while(J(pos)<>node and pos<getsize(J)) pos+=1 Find a new path cur:=node; newct:=0 in> 0) do forall(j in ISEC) if(TCOUNT(cur,j) > 0) then TCOUNT(cur,j)-=1 newct+=1; NEWJ(newct):=j cur:=j break end-if end-do ! Add the new path to main journey i:=getsize(J)-newct while(i>pos) do J(i+newct):=J(i) i-=1 end-do forall(j in 1..newct) J(pos+j):=NEWJ(j) returned:=newct end-function end-model