NETWORK FLOW

Introduction

      Problem Introduction

wikipedia

Graph: A directed graph G(V,E)

Supply & Target: supply(S) and target(T). We want to send from supply to target, there can be infinite supply avaliable.

Capacity: Each edge has some capacity c(x,y)

Flow: The actual amount we send is called flow f(x,y). And it cannot exceed capacity. 0 ≤ c(x,y) ≤ f(x,y).

Flow Conservation: For each node that is not supply or target, the incoming flow is equal to outgoing flow.

Value: The value |f| of a flow f is defined as:

      |f| = ∑v in V f(s,v) - ∑v in V f(v,s)

      That is the total flow out of source - the total flow into source

      It is trivial that we want to minimize the flow going back to source.

Output: Compute flow on each edge such that we have maximum flow coming to target.

S V1 V2 V3 V4 T

Yuye.Jiang@tufts.edu       Comp150-ALG-Summer2020