phase phase#1 "并发发起 50 个独立 worker"
phase phase#2 "汇总 50 个 worker 的产物"
node phase#1@1 mark phase=phase#1
node ask#1@1 issue site=ask#1 phase=phase#1
node phase#2@1 mark phase=phase#2
node ask#2@1 issue site=ask#2 phase=phase#2
edge entry -> phase#1@1 next
edge phase#1@1 -> ask#1@1 fork
edge ask#1@1 -> phase#2@1 join
edge phase#2@1 -> ask#2@1 next
edge ask#2@1 -> sink jump via=return
phase-edge entry -> phase#1 next
phase-edge phase#1 -> phase#2 join
phase-edge phase#2 -> sink jump via=return
