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- 乐观运动积极向上
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MODEL:
: m' A# q( J0 }/ n( ?( t( y: [. I, @) Q1 ]1 N
! The Vehicle Routing Problem (VRP); ) z K5 P w' \& M$ u q
" K) Y9 w5 V8 G, h! M!************************************;
1 b# y% Z# ^4 q& w" X! WARNING: Runtimes for this model ;
- Q6 x. |6 g6 g l* ^: B! increase dramatically as the number;
/ h) J9 i7 z+ w0 [6 U2 J( E0 B! of cities increase. Formulations ;5 `% ^9 n% Y) d2 B
! with more than a dozen cities ;" `& {/ W( u, B
! WILL NOT SOLVE in a reasonable ;9 i( O6 I$ y9 O' U
! amount of time! ;
! t5 X3 K7 U( Z- E O!************************************;
, B* F# p3 C2 @: o) \7 F7 U& w6 A8 |, O
SETS:- v( e- X) k1 r5 u5 D
! Q(I) is the amount required at city I,$ n5 j% K! B- v
U(I) is the accumulated delivers at city I ;
+ ^- d9 Z) a8 Q/ M ~$ | CITY/1..8/: Q, U;: v9 w* L3 Q4 v9 \
7 V' Q" x' }0 g& @5 ]4 B
! DIST(I,J) is the distance from city I to city J
7 D, e/ \" N; g7 `; A `3 I' [, o X(I,J) is 0-1 variable: It is 1 if some vehicle
' \6 Z& a7 M6 ^ travels from city I to J, 0 if none;
5 G/ O) Z( ?) t CXC( CITY, CITY): DIST, X;
j. N2 }) p* ]8 j! h, | ENDSETS& M% W% n! f7 @; Q( N( |4 C& G
6 N9 X* t, m8 n- v DATA:
6 ?. `1 f& ?8 K9 M, K8 C ! city 1 represent the common depo;" [6 L/ s' O+ a5 {9 y/ a/ @; u( s
Q = 0 6 3 7 7 18 4 5;
% u& d2 E! R1 ^3 n; f$ t! F( D$ z( F' q( f+ c# [
! distance from city I to city J is same from city
t& j( e& B! }( }6 h4 ?& v8 ? J to city I distance from city I to the depot is
8 Z6 O$ Y* d+ S- j# F$ {- `2 y 0, since the vehicle has to return to the depot;
0 u0 X4 `$ `7 N6 X6 E* p9 O( b& B$ O6 d
DIST = ! To City;- A% n2 g6 E' ^0 K
! Chi Den Frsn Hous KC LA Oakl Anah From;
- u7 t& [" _' `1 R 0 996 2162 1067 499 2054 2134 2050!Chicago; o- [& O' Z0 G) T9 n- B; t" h
0 0 1167 1019 596 1059 1227 1055!Denver; B* E5 b2 _0 Q: L' x
0 1167 0 1747 1723 214 168 250!Fresno;
) ]& w3 \' G; p' r5 g+ x. N! l0 y 0 1019 1747 0 710 1538 1904 1528!Houston;
9 t. ?9 u# |* b9 E8 K 0 596 1723 710 0 1589 1827 1579!K. City;4 X, M1 R' h( d8 l
0 1059 214 1538 1589 0 371 36!L. A.;/ _# d: Z3 m) ~3 M8 M- e$ G) M
0 1227 168 1904 1827 371 0 407!Oakland;
& D/ x$ F$ s. G f1 } 0 1055 250 1528 1579 36 407 0;!Anaheim;
# U$ v9 p2 ~6 t
+ k# e E) ^/ b ! VCAP is the capacity of a vehicle ;5 W3 J; m* k; P( h+ P" U
VCAP = 18;
% N; I, m' [7 r4 ?0 w7 i* j/ {: }( P' M) t ENDDATA
# X6 \5 h3 R( Z2 G/ O5 W1 D$ G2 _, B0 [$ l
! Minimize total travel distance;
# P* r+ ?$ A1 A3 m: \, C- c' { MIN = @SUM( CXC: DIST * X);- b* F% [3 r+ @
6 f2 n& r- F/ D0 j9 G' r
! For each city, except depot....; A7 \* n3 Z/ H: b8 g$ b
@FOR( CITY( K)| K #GT# 1:
. b; L4 T& {1 D, ^! |7 K' J2 B0 j M. z2 h' a8 s t/ v
! a vehicle does not travel inside itself,...;$ k9 \) O! y5 W/ ]
X( K, K) = 0;" @! p- ]5 `+ s9 S( \
) B- K: z5 S) L' A
! a vehicle must enter it,... ;/ v3 F, w' |! X* B" c* k* f+ w
@SUM( CITY( I)| I #NE# K #AND# ( I #EQ# 1 #OR#0 U: } w$ w( u9 \
Q( I) + Q( K) #LE# VCAP): X( I, K)) = 1;0 U5 ~) R' U) r" K8 u& o( w
6 L; O% ~3 e5 Z/ P8 q1 `
! a vehicle must leave it after service ;
* @- _4 {5 a8 `$ b! e% s, s7 z4 c @SUM( CITY( J)| J #NE# K #AND# ( J #EQ# 1 #OR#. ~4 h G U* j8 Y
Q( J) + Q( K) #LE# VCAP): X( K, J)) = 1;
1 U# C: {/ \+ f/ `! V* ?" j5 {0 W8 e. t) u* w# |4 y
! U( K) is at least amount needed at K but can't % J$ P' d4 \. T7 |1 B" k
exceed capacity;! |9 u8 m; i& j$ R9 D$ V' h
@BND( Q( K), U( K), VCAP);
8 ~7 i# Y3 B2 g: r+ d% q: O6 B) k
! If K follows I, then can bound U( K) - U( I);3 K+ D3 F4 D& A/ V3 A
@FOR( CITY( I)| I #NE# K #AND# I #NE# 1: 2 p5 u% R' f6 G, o
U( K) >= U( I) + Q( K) - VCAP + VCAP *
3 X5 Q" _/ A; C& p ( X( K, I) + X( I, K)) - ( Q( K) + Q( I))
4 z( v5 C' X. G: n * X( K, I);+ X& I2 {5 p" \5 F6 @4 t+ w$ G. k# \
);6 |/ P5 D& ^# ?# |7 `
; D5 e% ?0 A- D0 q: ]: d& T/ F" N, R ! If K is 1st stop, then U( K) = Q( K);
# w1 Y/ D3 |9 }6 Q$ L U( K) <= VCAP - ( VCAP - Q( K)) * X( 1, K);, t6 E* D6 B2 t* {% ]& A
6 q6 N/ I* Z' S
! If K is not 1st stop...;
" O/ e. m% l1 h1 q0 e3 [1 r U( K)>= Q( K)+ @SUM( CITY( I)| / ^/ E) Y$ @8 t. `
I #GT# 1: Q( I) * X( I, K));
+ l& d$ T( u; h! _* y! q );
! v! A6 w& \( r$ m
$ p# F( C8 u0 a. q ! Make the X's binary;6 y7 c; ^- M. H+ G
@FOR( CXC: @BIN( X));
6 E) Z5 @# |' L2 s. O9 W8 ?0 k. w. R
: q8 |$ t$ M- b9 B ! Minimum no. vehicles required, fractional 0 ]8 T6 L8 c( Y1 V
and rounded;
4 {: E/ R# @% J9 n6 l8 \/ @4 o$ l) S- v VEHCLF = @SUM( CITY( I)| I #GT# 1: Q( I))/ VCAP;8 Q9 j0 R5 {5 d9 @
VEHCLR = VEHCLF + 1.999 -
' ^- y3 A. p' `& r/ K/ i4 f @WRAP( VEHCLF - .001, 1);
& ~6 x& K k: c0 _/ |& z2 `* L4 m/ |& S4 s! f4 X& ^+ W
! Must send enough vehicles out of depot;
* r& m3 K5 G& n* s6 _ @SUM( CITY( J)| J #GT# 1: X( 1, J)) >= VEHCLR;
1 j. e, R) {3 h END# v/ E5 C4 @- N# F# G
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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