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MODEL:
( H) B6 x/ F3 p! \% n8 Z, T# I, A' H4 J& ]5 Q' d1 n9 Z& ]
! The Vehicle Routing Problem (VRP); / l6 k/ E4 g. e' U
& W& t$ }" f* t, C) B& y
!************************************;3 e R" Y9 D* x
! WARNING: Runtimes for this model ;- q9 d- P/ z; Y: C
! increase dramatically as the number;& s+ t$ Y" [; n
! of cities increase. Formulations ;
# S* p; l6 ^: r: s- S5 r! with more than a dozen cities ;# \) v8 Q" ^8 Q
! WILL NOT SOLVE in a reasonable ;2 ^8 J3 l- I+ ~ Q9 U. \/ i; M
! amount of time! ;
" G" H( g8 x8 T1 }! D3 R!************************************;
' E0 \/ q) o- X" u
9 u5 F8 O9 z0 n/ Y) a SETS:: h8 q, a+ r) _- a- \3 M
! Q(I) is the amount required at city I,0 b/ l5 ]* J+ ^( e2 \& L
U(I) is the accumulated delivers at city I ;- |+ c0 c% U' T# q
CITY/1..8/: Q, U;) S% Z0 _2 y$ Y" B5 X$ M# X! i5 S% H
1 Y9 o+ `) N# ?" I- V" }9 ] ! DIST(I,J) is the distance from city I to city J5 t; ?2 G) u7 J/ {) n# ?( H
X(I,J) is 0-1 variable: It is 1 if some vehicle2 \% A( e6 h# Y4 E
travels from city I to J, 0 if none;
! b7 Y; U0 E9 R$ k" a CXC( CITY, CITY): DIST, X;
$ t% \' [7 T+ H! C, h! n' P ENDSETS
3 f; `' l' ^+ ~5 x1 P, t, A! ]. S% H! i( F7 }
DATA:8 a/ q, Z" h, _* q4 @2 o5 \# n$ g
! city 1 represent the common depo;$ Y) u0 O5 U5 Q
Q = 0 6 3 7 7 18 4 5;6 \0 N. s; D: x; F; `& A
7 M+ ]5 H6 ~1 L( v+ n4 l
! distance from city I to city J is same from city
: W$ G& A- j# l: \ J to city I distance from city I to the depot is8 b" Z p7 k* T; Y$ O
0, since the vehicle has to return to the depot;
" m6 s4 D! ^9 p0 W. R+ B9 k
( g9 R, W* l$ v. T8 k; }1 J! f DIST = ! To City;) T7 u6 o5 V# r m2 b
! Chi Den Frsn Hous KC LA Oakl Anah From;
' _6 `# q( ? w/ s ~2 U' V 0 996 2162 1067 499 2054 2134 2050!Chicago;
; D/ o9 P# g4 x; u! F: \& e% u 0 0 1167 1019 596 1059 1227 1055!Denver;
9 P( S/ z. B& L4 ^ 0 1167 0 1747 1723 214 168 250!Fresno;
" Y0 s; I* Y5 i: c% E7 n 0 1019 1747 0 710 1538 1904 1528!Houston;! B! N% q4 l8 c2 u% F8 B+ L
0 596 1723 710 0 1589 1827 1579!K. City;
2 z% [3 K0 [' K- \3 r) l2 \9 Y 0 1059 214 1538 1589 0 371 36!L. A.;
' Y0 K7 n0 j1 N3 U, m7 w6 Y 0 1227 168 1904 1827 371 0 407!Oakland;5 v6 f7 {- S/ R- f% m
0 1055 250 1528 1579 36 407 0;!Anaheim;
4 X, \3 o7 X K5 R z
% z2 O% E0 V5 w+ P+ l! X* ` ! VCAP is the capacity of a vehicle ;) M* |& j; S3 [, k% O7 }" U9 v
VCAP = 18;
" C, O" ?# |1 Z* a6 v7 i0 U ENDDATA% b0 `2 F+ k9 V6 K* P0 D. s+ K
" x* X5 T! \/ P: h2 v0 ]
! Minimize total travel distance;
' \6 H. g0 U$ N4 z2 K MIN = @SUM( CXC: DIST * X);
1 }" Z8 C5 T# p# q) i$ K0 _8 e; v) h- A' G+ A
! For each city, except depot....;
/ O/ V1 p* s' Y7 v3 n* [: R3 Q @FOR( CITY( K)| K #GT# 1:
8 e; A8 \& N0 N( x% V1 I0 e8 I( \" n7 ~ t' }$ G
! a vehicle does not travel inside itself,...;) \. c. v! d3 |, M5 j' P4 a
X( K, K) = 0;4 x5 _. n) b" @; }' X
, _) k- @6 O9 J1 n2 p1 E7 l/ e
! a vehicle must enter it,... ;
! o8 F. S e& M7 Z6 u; L @SUM( CITY( I)| I #NE# K #AND# ( I #EQ# 1 #OR#3 W1 U1 }4 [& i' }9 j( w& Q( y0 ~
Q( I) + Q( K) #LE# VCAP): X( I, K)) = 1;. t5 G3 K- b3 Q4 U% H4 O/ @' i
% `, z! g0 j1 p, i6 T8 h5 @
! a vehicle must leave it after service ;
: O z7 d3 e# m" x @SUM( CITY( J)| J #NE# K #AND# ( J #EQ# 1 #OR#
. l% e" N/ X) X3 e' {# `( b3 v, ] Q( J) + Q( K) #LE# VCAP): X( K, J)) = 1;
, F) Q1 T/ s5 ], Q; _6 P5 D# y
0 [0 E' s/ W' V o$ i9 ~- W) O ! U( K) is at least amount needed at K but can't
4 J: K) L0 Z& a$ G# G; I exceed capacity;2 j4 `6 `/ O2 P- \+ X! J$ M- l
@BND( Q( K), U( K), VCAP);3 }" y& f/ b+ U( `; C
5 S3 S7 m) W; O! j2 Z4 W, Q ! If K follows I, then can bound U( K) - U( I);
, N7 a; e' l9 N @FOR( CITY( I)| I #NE# K #AND# I #NE# 1:
/ Y" ?8 V$ \6 I, i) x/ v U( K) >= U( I) + Q( K) - VCAP + VCAP * . K7 w' r2 H' W
( X( K, I) + X( I, K)) - ( Q( K) + Q( I))
" x5 ?1 M% r- m7 d * X( K, I);+ Q! f5 @9 J$ F: M* o
);1 w ?) l# y2 v2 D* `/ c
2 Z, x- W1 k8 j& l+ U5 X1 F ! If K is 1st stop, then U( K) = Q( K);+ p$ |- ^5 O6 u
U( K) <= VCAP - ( VCAP - Q( K)) * X( 1, K);# ]5 h* a2 ]6 I+ Z% P- a1 r: L) N" i
/ V$ O% R: J- M) ]6 D9 O. K ! If K is not 1st stop...;
: ]( b0 b( K" a% T6 E) f A U( K)>= Q( K)+ @SUM( CITY( I)|
. \( O. \- \% o+ U I #GT# 1: Q( I) * X( I, K));
2 U, P7 Z; e8 v6 K: D1 } );+ a6 X- o! a1 J7 J8 f
0 {. B: [! k9 O% i( a$ s ! Make the X's binary;
* A" C; Y$ O/ t/ C @FOR( CXC: @BIN( X));
$ W- l; l: n V0 K9 n9 r. M. H% h6 D8 |; h/ _1 b0 W
! Minimum no. vehicles required, fractional
; s9 V/ X* l/ e0 ^& i1 s0 p: Q; Y and rounded;
5 T; w8 f; r" @ VEHCLF = @SUM( CITY( I)| I #GT# 1: Q( I))/ VCAP;
1 Z p5 z7 O: h* W# M" s VEHCLR = VEHCLF + 1.999 -
( `8 Q3 e8 |0 G7 P @WRAP( VEHCLF - .001, 1);) T6 k. z, J& b, R
, R; H3 c$ h. \6 v- z* a- U* ^ ! Must send enough vehicles out of depot;
8 y& ~" y5 c" | @SUM( CITY( J)| J #GT# 1: X( 1, J)) >= VEHCLR;9 F- ~. A9 K, |' p
END& n8 {8 A/ I" W8 ?( Q
请问大家里面U(I)的公式如何理解啊 U(I)是城市I 的累积交付量么?谢谢 |
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