Regular　expression　matching　is　pivotal　in　numerous　network　applications.　With　the　ever-increasing　scale　of　data　center　traffic,　deploying　regular　expression　matching　modules　on　traditional　servers　struggles　to　meet　throughput　demands.　Emerging　programmable　switches　have　brought　new　prospects　for　high-speed　pattern　matching.　However,　deploying　regular　expression　matching　onto　programmable　switches　presents　the　challenge　of　space　explosion　incurred　by　compiling　regular　expressions　into　a　Deterministic　Finite　Automata　(DFA).　In　this　paper,　we　introduce　P4Rex,　a　regular　expression　matching　system　designed　for　programmable　switches.　P4Rex　synergistically　leverages　two　following　techniques:　an　efficient　regular　expression　grouping　algorithm　that　partitions　regular　expressions　into　different　groups　to　reduce　memory　consumption,　and　DFA　compression　technology　to　achieve　transition　sharing.　Experimental　results　demonstrate　that　P4Rex　exhibits　an　average　improvement　of　17%　and　maximum　improvement　of　30%　on　memory　consumption　compared　to　prior　regular　expression　grouping　schemes　and　saves　more　than　10x　memory　consumption　compared　to　deploying　DFA　directly　on　programmable　switch.　©　2024　Elsevier　B.V.