/// Debug functions used mainly to collect run-time statistics
-static int64_t hits[2], means[2];
+static std::atomic<int64_t> hits[2], means[2];
void dbg_hit_on(bool b) { ++hits[0]; if (b) ++hits[1]; }
void dbg_hit_on(bool c, bool b) { if (c) dbg_hit_on(b); }