ARM compatibility

include/dbscan/cell.h

@@ -173,6 +173,6 @@ struct cellHash {
 
   bool cas(eType* p, eType o, eType n) {
     return std::atomic_compare_exchange_strong_explicit(
-      reinterpret_cast<std::atomic<eType>*>(p), &o, n, std::memory_order_relaxed, std::memory_order_relaxed);
+      reinterpret_cast<std::atomic<eType>*>(p), &o, n, std::memory_order_acq_rel, std::memory_order_acquire);
   }
 };

include/dbscan/pbbs/ndHash.h

@@ -404,7 +404,7 @@ struct hashSimplePair {
   bool replaceQ(eType s, eType s2) {return 0;}//return s.second > s2.second;}
   bool cas(eType* p, eType o, eType n) {
     return std::atomic_compare_exchange_strong_explicit(
-      reinterpret_cast<std::atomic<eType>*>(p), &o, n, std::memory_order_relaxed, std::memory_order_relaxed);
+      reinterpret_cast<std::atomic<eType>*>(p), &o, n, std::memory_order_acq_rel, std::memory_order_acquire);
   }
 };
 

include/dbscan/pbbs/scheduler.h

@@ -88,23 +88,23 @@ struct Deque {
   Deque() : bot(0), age(age_t{0, 0}) {}
 
   void push_bottom(Job* job) {
-    auto local_bot = bot.load(std::memory_order_relaxed);      // atomic load
-    deq[local_bot].job.store(job, std::memory_order_relaxed);  // shared store
+    auto local_bot = bot.load(std::memory_order_acquire);      // atomic load
+    deq[local_bot].job.store(job, std::memory_order_release);  // shared store
     local_bot += 1;
     if (local_bot == q_size) {
       throw std::runtime_error("internal error: scheduler queue overflow");
     }
-    bot.store(local_bot, std::memory_order_relaxed);  // shared store
+    bot.store(local_bot, std::memory_order_release);  // shared store
     std::atomic_thread_fence(std::memory_order_seq_cst);
   }
 
   Job* pop_top() {
     Job* result = nullptr;
-    auto old_age = age.load(std::memory_order_relaxed);    // atomic load
-    auto local_bot = bot.load(std::memory_order_relaxed);  // atomic load
+    auto old_age = age.load(std::memory_order_acquire);    // atomic load
+    auto local_bot = bot.load(std::memory_order_acquire);  // atomic load
     if (local_bot > old_age.top) {
       auto job =
-          deq[old_age.top].job.load(std::memory_order_relaxed);  // atomic load
+          deq[old_age.top].job.load(std::memory_order_acquire);  // atomic load
       auto new_age = old_age;
       new_age.top = new_age.top + 1;
       if (age.compare_exchange_strong(old_age, new_age))
@@ -117,24 +117,24 @@ struct Deque {
 
   Job* pop_bottom() {
     Job* result = nullptr;
-    auto local_bot = bot.load(std::memory_order_relaxed);  // atomic load
+    auto local_bot = bot.load(std::memory_order_acquire);  // atomic load
     if (local_bot != 0) {
       local_bot--;
-      bot.store(local_bot, std::memory_order_relaxed);  // shared store
+      bot.store(local_bot, std::memory_order_release);  // shared store
       std::atomic_thread_fence(std::memory_order_seq_cst);
       auto job =
-          deq[local_bot].job.load(std::memory_order_relaxed);  // atomic load
-      auto old_age = age.load(std::memory_order_relaxed);      // atomic load
+          deq[local_bot].job.load(std::memory_order_acquire);  // atomic load
+      auto old_age = age.load(std::memory_order_acquire);      // atomic load
       if (local_bot > old_age.top)
         result = job;
       else {
-        bot.store(0, std::memory_order_relaxed);  // shared store
+        bot.store(0, std::memory_order_release);  // shared store
         auto new_age = age_t{old_age.tag + 1, 0};
         if ((local_bot == old_age.top) &&
             age.compare_exchange_strong(old_age, new_age))
           result = job;
         else {
-          age.store(new_age, std::memory_order_relaxed);  // shared store
+          age.store(new_age, std::memory_order_release);  // shared store
           result = nullptr;
         }
         std::atomic_thread_fence(std::memory_order_seq_cst);
@@ -246,7 +246,7 @@ struct scheduler {
   std::vector<Deque<Job>> deques;
   std::vector<attempt> attempts;
   std::vector<std::thread> spawned_threads;
-  std::atomic<int> finished_flag;
+  std::atomic<bool> finished_flag;
 
   // Start an individual scheduler task.  Runs until finished().
   template <typename F>

include/dbscan/pbbs/utils.h

@@ -292,7 +292,7 @@ template <class E1, class E2>
 template<typename eType>
 bool myCAS(eType* p, eType o, eType n) {
   return std::atomic_compare_exchange_strong_explicit(
-    reinterpret_cast<std::atomic<eType>*>(p), &o, n, std::memory_order_relaxed, std::memory_order_relaxed);
+    reinterpret_cast<std::atomic<eType>*>(p), &o, n, std::memory_order_acq_rel, std::memory_order_acquire);
 }
 
 template <class ET>

include/dbscan/pbbs/work_stealing_job.h

@@ -32,16 +32,16 @@ namespace parlay {
 
 struct WorkStealingJob {
   WorkStealingJob() {
-    done.store(false, std::memory_order_relaxed);
+    done.store(false, std::memory_order_release);
   }
   ~WorkStealingJob() = default;
   void operator()() {
-    assert(done.load(std::memory_order_relaxed) == false);
+    assert(done.load(std::memory_order_acquire) == false);
     execute();
-    done.store(true, std::memory_order_relaxed);
+    done.store(true, std::memory_order_release);
   }
   bool finished() {
-    return done.load(std::memory_order_relaxed);
+    return done.load(std::memory_order_acquire);
   }
   virtual void execute() = 0;
   std::atomic<bool> done;