Heterogeneous Attentions for Solving Pickup and Delivery Problem via Deep Reinforcement Learning

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文章目录


前言

论文阅读笔记:Heterogeneous Attentions for Solving Pickup and Delivery Problem via Deep Reinforcement Learning


一、PDP问题

定义:载具从仓库开始,依次访问所有取货节点和配送节点,只执行一次服务,最后返回仓库,尽可能地节省时间。注意,这里PDP允许连续的拾取或交付,或它们的混合,只要它满足优先约束。

n n n:客户请求数量
P = x i i = 1 n P=\\ x_i \\_i=1^n P=xii=1n:pickup node set
D = x i i = n + 1 2 n D=\\ x_i \\_i=n+1^2n D=xii=n+12n:delivery node set
x i x_i xi:pickup node
x n + 1 x_n+1 xn+1:delivery node,与 pickup node 为成对的,具有优先级关系
仓库:node 0
X = x 0 ∪ P ∪ D X=\\ x_0 \\ \\cup P \\cup D X=x0PD:complete node set
X ′ = x 2 n + 1 ∪ X = x i i = 0 2 n + 1 X'=\\ x_2n+1 \\ \\cup X =\\ x_i \\_i=0^2n+1 X=x2n+1X=xii=02n+1:其中 x 2 n + 1 x_2n+1 x2n+1为仓库的copy
c i \\ c_i \\ ci:包含 x i \\ x_i \\ xi二维坐标
v v v:载具,从 x i x_i xi全部运输到从 x i + n x_i+n xi+n(有无限的运输能力)
D i j D_ij Dij:表示节点 x i x_i xi到节点 x j x_j xj的欧氏距离
f f f为载具 v v v的速度
y i j ∈ 0 , 1 y_ij \\in \\ 0,1 \\ yij0,1:二元变量,指示载具 v v v是否直接从节点 x i x_i xi到节点 x j x_j xj
B i B_i Bi:表示节点 x i x_i xi的到达时间
M M M是一个足够大的数

为追求速度尽量快、距离尽量短,可以得到如下目标函数:
min ⁡ ∑ i ∈ X ∑ j ∈ X D i j f y i j \\min \\sum_i \\in X \\sum_j \\in X \\fracD_i jf y_i j miniXjXfDijyij
约束条件如下:
∑ j ∈ X y i j = 1 , i ∈ X ′ ∑ i ∈ X y i j = 1 , j ∈ X ′ B j ≥ B i + D i j f − M ( 1 − y i j ) , i ∈ X ′ , j ∈ X ′ B i + n ≥ B i + D i , i + n f , i ∈ P , i + n ∈ D y i j = 0 , 1 , i ∈ X ′ , j ∈ X ′ B i ≥ 0 , i ∈ X ′ \\beginaligned \\sum_j \\in X y_i j &=1, \\quad i \\in X^\\prime\\\\ \\sum_i \\in X y_i j &=1, \\quad j \\in X^\\prime\\\\ B_j & \\geq B_i+\\fracD_i jf-M\\left(1-y_i j\\right), \\quad i \\in X^\\prime, j \\in X^\\prime\\\\ B_i+n & \\geq B_i+\\fracD_i, i+nf, \\quad i \\in P, i+n \\in D\\\\ y_i j &=\\0,1\\, \\quad i \\in X^\\prime, j \\in X^\\prime \\\\ B_i & \\geq 0, \\quad i \\in X^\\prime \\endaligned jXyijiXyijBjBi+nyijBi=1,iX=1,jXBi+fDijM(1yij),iX,jXBi+fDi,i+n,iP,i+nD=0,1,iX,jUbuntu20.04 Attentions

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