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- 乐观运动积极向上
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MODEL:
7 V& L" q' @- q' `. P
$ u& L. t6 \1 r6 [8 ^0 n8 C! The Vehicle Routing Problem (VRP);
( F7 v% r: n7 ^3 u+ b, ]* n/ B) M: ~3 f. g6 _# M8 _ D+ A
!************************************;0 c! d) k$ X+ G% c: w
! WARNING: Runtimes for this model ;7 Q& M$ b3 g7 a( A3 h/ W4 W
! increase dramatically as the number;' ~$ l6 Z8 }" ~( q8 `
! of cities increase. Formulations ;
' g# i& w0 K$ E' Q, r1 O! with more than a dozen cities ;
0 Y- P4 Q6 b- c# s' G$ {! WILL NOT SOLVE in a reasonable ;" X& R+ m8 U) F$ f
! amount of time! ;3 z' m( N1 k% ~: [
!************************************;; A" f: a4 q [5 q3 Q4 [' `
2 X2 e' L. B4 X$ H8 C
SETS:
2 ^' `* }* a6 j, c* i5 j6 V ! Q(I) is the amount required at city I,
4 A' M B y% I0 l/ M8 i0 l U(I) is the accumulated delivers at city I ;
, S+ E1 q" r4 I CITY/1..8/: Q, U;0 x+ i- E3 ~' S. {- E/ ~7 f
( u0 p$ R* ~7 h, V2 {
! DIST(I,J) is the distance from city I to city J
) d' f3 t; d& G$ U X(I,J) is 0-1 variable: It is 1 if some vehicle
7 [1 ^& ~' V9 `1 q travels from city I to J, 0 if none;
( x. l1 T, r) l i3 p; u5 {# ` CXC( CITY, CITY): DIST, X;6 j9 j' K0 T) M
ENDSETS! Z# c( a9 W6 D) p' u3 T3 [- w6 ~8 x
" Y! |' P" D' x/ A) `( T. D9 D DATA:
: N8 I0 z0 H( Q) l- O+ E, \; F ! city 1 represent the common depo;1 S# F) Y2 P! o5 `" G; E: Z: m
Q = 0 6 3 7 7 18 4 5;& Z6 v% T, s; E4 F" N
7 ^; i6 F: H/ Y. ?* m ! distance from city I to city J is same from city4 p) I. [+ I* b. s- T
J to city I distance from city I to the depot is6 E* {& T M$ r0 n$ e9 J2 l" W
0, since the vehicle has to return to the depot;! ^; d* C1 _& c3 F8 i7 U
0 r; n( s" H2 K" k
DIST = ! To City;2 @: j2 C! B, i0 k0 U+ e
! Chi Den Frsn Hous KC LA Oakl Anah From;1 m& K. z- O0 s6 I2 J8 a
0 996 2162 1067 499 2054 2134 2050!Chicago;
) f: |, N3 [' k" Y2 O 0 0 1167 1019 596 1059 1227 1055!Denver;/ _9 |* p9 [& p, x+ t( ^
0 1167 0 1747 1723 214 168 250!Fresno;& j/ ?5 M4 j% }9 I
0 1019 1747 0 710 1538 1904 1528!Houston;
6 a: T5 \8 H$ z& Q0 A6 o& @- w 0 596 1723 710 0 1589 1827 1579!K. City;1 t) F$ u- @, d' Q7 j
0 1059 214 1538 1589 0 371 36!L. A.;
$ L4 q! r# @' d 0 1227 168 1904 1827 371 0 407!Oakland;! o! n* ?( K6 ^$ ^
0 1055 250 1528 1579 36 407 0;!Anaheim;
' ^" ~; ~2 \/ y( ~" K. J5 \0 c2 d- {. C. ~
! VCAP is the capacity of a vehicle ;
' r7 Z+ z3 c, m, U8 }: R( A5 X VCAP = 18;
T" b7 d) d3 S ENDDATA6 b3 i0 h6 m! Y; u) C% P) |
$ j3 M/ u* Y- F" H: u6 X3 @ ! Minimize total travel distance;% r j9 b/ {; E
MIN = @SUM( CXC: DIST * X);
+ M( w. V0 h4 y% P
8 Q( N3 O$ V0 H4 K1 c ! For each city, except depot....;
3 t3 d4 s+ Y( ~ @FOR( CITY( K)| K #GT# 1:
4 c, V P. ~& b0 ]( P. M6 U( [0 w& Y% b
" E6 x$ J5 F& ^" y% c9 \& W1 i$ G6 o ! a vehicle does not travel inside itself,...;
+ f: D$ E1 ^5 k" M1 i8 R X( K, K) = 0;
. _1 x& e2 x* f6 I. D% N: n
+ F0 e' h; z0 n& y" I& m ! a vehicle must enter it,... ;
) [4 ?% J7 E/ J% x; p5 D0 B+ F @SUM( CITY( I)| I #NE# K #AND# ( I #EQ# 1 #OR#5 L9 M, o, W+ n+ u. L3 v; M( O1 }- s
Q( I) + Q( K) #LE# VCAP): X( I, K)) = 1;
) S' G6 ^) S+ \; Q. |# s" `) d3 ^' p2 P
! a vehicle must leave it after service ;- q2 Q @( V* p" w- W# e
@SUM( CITY( J)| J #NE# K #AND# ( J #EQ# 1 #OR# [8 a, \7 d+ c3 K t& t( p0 m
Q( J) + Q( K) #LE# VCAP): X( K, J)) = 1;
' h1 x. E- [: ?5 D8 `3 ] J# H" e# v8 K: ^. b; U
! U( K) is at least amount needed at K but can't
/ v4 h9 I" N# W+ Q, a" V* q exceed capacity;
- r% T0 }! Z$ j$ |) t. ~ @BND( Q( K), U( K), VCAP);
* g$ K' [! [ @, [% o+ m
' P7 u& J& a, C2 |' g' p& ` ! If K follows I, then can bound U( K) - U( I);
6 D5 o9 J+ r& K. o: f @FOR( CITY( I)| I #NE# K #AND# I #NE# 1:
2 x6 H8 b; @3 A# R( n2 U9 m7 d! }( n U( K) >= U( I) + Q( K) - VCAP + VCAP *
* b8 x3 U/ f& _$ q" d ( X( K, I) + X( I, K)) - ( Q( K) + Q( I))' q0 @$ t q4 S2 l7 ?( V2 n
* X( K, I);6 }+ T _( p$ @- }( f
);
1 f' k( t1 n* v- k9 i! O
! E* U% S, H8 G, Y* f1 P ! If K is 1st stop, then U( K) = Q( K);
V1 \* F+ f; L% K; Q U( K) <= VCAP - ( VCAP - Q( K)) * X( 1, K);
1 U# F7 X- V* o% q8 N7 M
+ @# F3 g0 N8 e* P" F) A ! If K is not 1st stop...;4 q, Q( ]! m, h
U( K)>= Q( K)+ @SUM( CITY( I)|
( x' b/ `, L5 ?8 H I #GT# 1: Q( I) * X( I, K));# c% L; i* Q* A/ T- \5 Y0 k: k
);3 Y% O3 i0 d+ H; _( |) X/ @
1 |; g) _( i: y ! Make the X's binary;
) V/ Q. m# O# K9 E( u @FOR( CXC: @BIN( X));
" v) r* Y. v" m- N. M6 z$ z
7 c6 {" d% h {$ T8 L! Q; D2 @ ! Minimum no. vehicles required, fractional
) U; F3 K; f1 B, Q% Z/ o | and rounded;
& c# }' K6 v1 b VEHCLF = @SUM( CITY( I)| I #GT# 1: Q( I))/ VCAP;
' P& L% S' t7 | VEHCLR = VEHCLF + 1.999 - 2 N1 L- S5 o" d0 r/ L: {" p4 s/ R
@WRAP( VEHCLF - .001, 1);/ e4 s( v6 Y9 X2 L0 I( U" t
: z b( e( a# P" ~# ]8 `
! Must send enough vehicles out of depot;; N, T( M7 e+ N7 k3 [! c
@SUM( CITY( J)| J #GT# 1: X( 1, J)) >= VEHCLR;
6 U; u& |* X! b7 Z4 Q$ ^9 ~ END" {: N' x( E+ E% N ] N
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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