In　this　paper,　an　adaptive　algorithm　is　proposed　to　perform　electromigration　(EM)　assessment　for　full-chip　power/ground　networks.　Based　on　the　eigenfunction　solutions,　the　proposed　method　improves　the　efficiency　by　properly　selecting　the　eigenfunction　terms　and　utilizing　the　closed-form　eigenfunctions　for　commonly　seen　interconnect　wires　such　as　T-shaped　or　cross-shaped　wires.　It　is　demonstrated　that　the　proposed　method　can　trad-off　well　among　the　accuracy,　efficiency　and　applicability　of　the　eigenfunction　based　methods.　The　experimental　results　show　that　the　proposed　method　is　about　three　times　faster　than　the　finite　difference　method　and　other　eigenfunction　based　methods.　©　2020　IEEE.