initial commit, 4.5 stable

thirdparty/embree/common/algorithms/parallel_map.h

@@ -0,0 +1,85 @@
+// Copyright 2009-2021 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include "parallel_sort.h"
+
+namespace embree
+{
+  /*! implementation of a key/value map with parallel construction */
+  template<typename Key, typename Val>
+  class parallel_map
+  {
+    /* key/value pair to build the map */
+    struct KeyValue
+    {
+      __forceinline KeyValue () {}
+
+      __forceinline KeyValue (const Key key, const Val val)
+	: key(key), val(val) {}
+
+      __forceinline operator Key() const {
+	return key;
+      }
+
+    public:
+      Key key;
+      Val val;
+    };
+
+  public:
+    
+    /*! parallel map constructors */
+    parallel_map () {}
+
+    /*! construction from pair of vectors */
+    template<typename KeyVector, typename ValVector>
+      parallel_map (const KeyVector& keys, const ValVector& values) { init(keys,values); }
+
+    /*! initialized the parallel map from a vector with keys and values */
+    template<typename KeyVector, typename ValVector>
+      void init(const KeyVector& keys, const ValVector& values) 
+    {
+      /* reserve sufficient space for all data */
+      assert(keys.size() == values.size());
+      vec.resize(keys.size());
+      
+      /* generate key/value pairs */
+      parallel_for( size_t(0), keys.size(), size_t(4*4096), [&](const range<size_t>& r) {
+	for (size_t i=r.begin(); i<r.end(); i++)
+	  vec[i] = KeyValue((Key)keys[i],values[i]);
+      });
+
+      /* perform parallel radix sort of the key/value pairs */
+      std::vector<KeyValue> temp(keys.size());
+      radix_sort<KeyValue,Key>(vec.data(),temp.data(),keys.size());
+    }
+
+    /*! Returns a pointer to the value associated with the specified key. The pointer will be nullptr of the key is not contained in the map. */
+    __forceinline const Val* lookup(const Key& key) const 
+    {
+      typename std::vector<KeyValue>::const_iterator i = std::lower_bound(vec.begin(), vec.end(), key);
+      if (i == vec.end()) return nullptr;
+      if (i->key != key) return nullptr;
+      return &i->val;
+    }
+
+    /*! If the key is in the map, the function returns the value associated with the key, otherwise it returns the default value. */
+    __forceinline Val lookup(const Key& key, const Val& def) const 
+    {
+      typename std::vector<KeyValue>::const_iterator i = std::lower_bound(vec.begin(), vec.end(), key);
+      if (i == vec.end()) return def;
+      if (i->key != key) return def;
+      return i->val;
+    }
+
+    /*! clears all state */
+    void clear() {
+      vec.clear();
+    }
+
+  private:
+    std::vector<KeyValue> vec;    //!< vector containing sorted elements
+  };
+}