False sharing in atomic array
Review this C++ per-thread counter array used in a hot parallel loop.
It's correct but a senior reviewer flagged it. What's the concurrency-related problem?
What a strong answer looks like
Separate real bugs from style. Rank issues by severity, point at the root cause rather than the symptom, and suggest a concrete fix, specific and kind.
0:00 of about 40 min
Mark a line and say what kind of problem it is.0 findings
1struct Counters {
2 std::atomic<long> hits[8]; // one slot per worker thread
3};
4
5void worker(Counters& c, int tid, const std::vector<int>& work) {
6 for (int v : work) {
7 if (heavy_predicate(v))
8 c.hits[tid].fetch_add(1, std::memory_order_relaxed); // (1)
9 }
10}
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
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