2 docs tagged with "cooperative-groups"

Warp-Level Primitives and Block Synchronization both work, but both lean on implicit context there is no implicit lockstep assumption left to break, because every operation states which threads it applies to.

syncthreads() barriers a block; cluster.sync() barriers a cluster; neither reaches every block in a grid. Some algorithms genuinely need that — a multi-pass iterative solver that must finish writing generation *N* everywhere before any block reads generation *N* for generation *N+1*, for instance — and the usual answer, launching a second kernel between the passes, has real cost when the intermediate state is large and expensive to leave and re-establish. Grid-wide synchronization exists for that case, but it is not simply "a bigger syncthreads()": it comes with a hardware constraint that shapes the whole launch around it.