: v6 y+ H5 U" B% H& h!************************************; 8 t3 s6 S. d* J! WARNING: Runtimes for this model ;& ^, V, d# H+ t! I$ y
! increase dramatically as the number;& p5 c" R2 C5 f9 A. U2 d
! of cities increase. Formulations ;3 K/ D2 D, K2 o
! with more than a dozen cities ;; Q" j* v* l1 ?4 t& ^" R. w6 q
! WILL NOT SOLVE in a reasonable ; 9 o0 E j6 G. s* c9 K/ ~! amount of time! ;- Z5 k" Z1 N5 W& o) @$ ~
!************************************;) [+ D# N4 E% r; V
' ^. V. H- \6 I# O2 J! k6 { SETS:5 C* J* T8 S3 b0 E% k* T
! Q(I) is the amount required at city I, : b/ h- b' A) U8 Z8 _+ q" ? U(I) is the accumulated delivers at city I ;" K' J) H. O# Y) Y
CITY/1..8/: Q, U;3 z8 v# W7 ^3 C
- ^" u! h1 X/ y! N. e& ^
! DIST(I,J) is the distance from city I to city J# p" v. P- L |5 c9 b" f( n
X(I,J) is 0-1 variable: It is 1 if some vehicle' y3 W. i5 r- F4 E& k/ V
travels from city I to J, 0 if none; 1 J8 j; C6 e7 l3 T) D CXC( CITY, CITY): DIST, X;/ u2 k! j6 Y: K
ENDSETS ' x2 }4 A. P6 K l. G7 c- d7 q$ u; o9 h
DATA:2 g2 }% f: `' {+ v; ~3 y7 i
! city 1 represent the common depo; / t" l5 q2 b9 K, N2 F& ` Q = 0 6 3 7 7 18 4 5; 3 i3 T; W/ n- M3 G3 o w1 p! L' v2 R+ N$ X6 |, u; G9 I0 g
! distance from city I to city J is same from city $ n; Z& P8 Z9 }6 P( N; E! R) ~ J to city I distance from city I to the depot is f# d' p' r; {& Q" r7 T$ i 0, since the vehicle has to return to the depot; , T# U$ `* W/ l0 `; R. X! [1 Z& U/ D& B5 m/ N6 M6 K2 H' y
DIST = ! To City; S6 y, ?: C7 g9 {& ^% `
! Chi Den Frsn Hous KC LA Oakl Anah From;2 p8 R8 p# L; e/ m/ ^. n9 y+ ~& B. V
0 996 2162 1067 499 2054 2134 2050!Chicago;2 _& i+ ?# u1 c+ [* q! j
0 0 1167 1019 596 1059 1227 1055!Denver;+ x" W I9 i7 |9 |5 o5 I
0 1167 0 1747 1723 214 168 250!Fresno; 2 Z% |' f& ~% k" t# o2 k 0 1019 1747 0 710 1538 1904 1528!Houston; 8 X7 J- T3 W m1 Q- L& f; v 0 596 1723 710 0 1589 1827 1579!K. City; 8 t9 S O9 m7 S% Y. G& T/ B) } 0 1059 214 1538 1589 0 371 36!L. A.; - z- j1 f) f$ s! t% y 0 1227 168 1904 1827 371 0 407!Oakland;3 I2 V8 y: ]$ X! s2 q6 ~$ ^
0 1055 250 1528 1579 36 407 0;!Anaheim;/ q$ O1 ~: z+ ^/ E; q; m' k& x' \. ?
7 ?" N d6 ~5 e1 B" b6 c: ? ! VCAP is the capacity of a vehicle ;* W$ n7 F* C' D& W$ ^
VCAP = 18; ' t9 w ~2 i# v( ~7 A; I# {# Z ENDDATA# S$ ^. R$ C* O; q/ \
" F6 W* }" P/ e6 B ! Minimize total travel distance; 0 C" ?2 l; U) j4 [6 L MIN = @SUM( CXC: DIST * X);. v, l3 }+ v: A8 q8 z* h2 o
3 ?* _" z6 ^. ?6 p
! For each city, except depot....; 7 q+ B$ { x: u3 [" z H @FOR( CITY( K)| K #GT# 1:5 S% G5 g# T: \6 {* U1 s
( x5 `9 f2 O8 {/ r
! a vehicle does not travel inside itself,...; ' _# m1 l8 H% w* p+ y X( K, K) = 0; 5 A9 C8 }# n4 E. A4 ?& ?5 w4 L2 E% r3 t# J/ b
! a vehicle must enter it,... ;( l4 }# G/ k' p, Z& o
@SUM( CITY( I)| I #NE# K #AND# ( I #EQ# 1 #OR#/ _/ _* K! i# w' q" a% {$ u
Q( I) + Q( K) #LE# VCAP): X( I, K)) = 1;. H; L" v3 l* ? z, u& k" o. l
7 A) d7 H' _# N3 c# {
! a vehicle must leave it after service ; , ?2 A9 Z* v1 s r& n* l6 H @SUM( CITY( J)| J #NE# K #AND# ( J #EQ# 1 #OR#1 N Y1 k0 T4 |
Q( J) + Q( K) #LE# VCAP): X( K, J)) = 1;, Y7 q R O: L
5 W* c6 W5 D; r' E! j: X ! U( K) is at least amount needed at K but can't 9 R" C6 Q! N) K% F exceed capacity; $ j9 f, A1 |9 D( X0 y @BND( Q( K), U( K), VCAP); & n* n4 u5 M- K' b0 V 5 L" n8 E, p0 V$ ] n$ V, M8 X4 @+ D1 @ ! If K follows I, then can bound U( K) - U( I);! h6 R7 m! f& E+ q# E
@FOR( CITY( I)| I #NE# K #AND# I #NE# 1: * W' Y) A" _5 T; V$ P0 u. A U( K) >= U( I) + Q( K) - VCAP + VCAP * 0 w& P3 w4 ]3 y. q ( X( K, I) + X( I, K)) - ( Q( K) + Q( I))0 \0 _) r" z' f6 n
* X( K, I);: R; ]& Q8 L9 R! F' V# |8 M
);6 S+ @7 q# O. n, z+ y1 n8 q3 a( M
% [9 a/ `- D, F r/ T" O' b# s
! If K is 1st stop, then U( K) = Q( K);9 V/ q9 B1 s4 @, {, D+ o9 U
U( K) <= VCAP - ( VCAP - Q( K)) * X( 1, K); % p+ L6 u4 i* t6 @" S/ B % Y% y1 @0 w/ x ! If K is not 1st stop...; % |; w# g9 c" n7 B$ K8 S U( K)>= Q( K)+ @SUM( CITY( I)| : z* X; S: V* T/ K3 A5 Y$ W I #GT# 1: Q( I) * X( I, K)); . n: Z9 q0 I. \8 @/ S ); ' f9 J; `3 ?* Y! E" h 4 ~/ j4 O8 Q R m& ?: q ! Make the X's binary; * d) t2 w; l. i @FOR( CXC: @BIN( X));/ e+ I9 b$ Z* A' q8 k
8 I2 R, j. _# b b8 M0 T ! Minimum no. vehicles required, fractional . `' u; ^. J. j ?7 q4 J' T
and rounded; , l" L* E! Z( C VEHCLF = @SUM( CITY( I)| I #GT# 1: Q( I))/ VCAP; x3 V0 v% F( [1 ?0 A+ |" F/ X
VEHCLR = VEHCLF + 1.999 - & h# [$ `; Y3 t5 W0 C7 N( g" v
@WRAP( VEHCLF - .001, 1);) V0 K9 R5 \- K' \6 M) P