Switch from ThreadPool to a simpler thread map for containers.

1 files changed, 55 insertions, 0 deletions

diff --git a/src/thread_utils.h b/src/thread_utils.h
new file mode 100644
index 00000000..fe096a36
--- /dev/null
+++ b/src/thread_utils.h
@@ -0,0 +1,55 @@
+#ifndef MO2_THREAD_UTILS_H
+#define MO2_THREAD_UTILS_H
+
+#include <mutex>
+#include <thread>
+
+namespace MOShared {
+
+/**
+ * @brief Apply the given callable to each element between the two given iterators
+ *     in a parallel way.
+ *
+ * The callable should be independent, or properly synchronized, and the source of
+ * the range should not change during this call.
+ *
+ * @param start Beginning of the range.
+ * @param end End of the range.
+ * @param callable Callable to apply to every element of the range. See std::invoke
+ *     requirements. Must be copiable.
+ * @param nThreads Number of threads to use.
+ *
+ */
+template <class It, class Callable>
+void parallelMap(It begin, It end, Callable callable, std::size_t nThreads) {
+  std::vector<std::thread> threads(nThreads);
+
+  std::mutex m;
+  for (auto &thread: threads) {
+    thread = std::thread([&m, &begin, end, callable]() {
+      while (true) {
+        decltype(begin) it;
+        {
+          std::scoped_lock lock(m);
+          if (begin == end) {
+            break;
+          }
+          it = begin++;
+        }
+        if (it != end) {
+          std::invoke(callable, *it);
+        }
+      }
+    });
+  }
+
+
+  // Join everything:
+  for (auto& t : threads) {
+    t.join();
+  }
+}
+
+}
+
+#endif