If I have a C++ program with OpenMP parallelization, where different threads constantly use some small shared array only for reading data from it, does false sharing occur in this case? in other words, is false sharing related only to memory write operations, or it can also happen with memory read operations.
Typically used cache coherence protocols, such as MESI (modified, exclusive, shared, invalid), have a specific state for cache lines called "shared". Cache lines are in this state if they are read by multiple processors. Each processor then has a copy of the cache line and can safely read from it without false-sharing. On a write, all processors are informed to invalidate the cache line which is the main cause for false-sharing