initial commit, 4.5 stable

thirdparty/embree/common/algorithms/parallel_reduce.h

@@ -0,0 +1,146 @@
+// Copyright 2009-2021 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+
+#pragma once
+
+#include "parallel_for.h"
+
+namespace embree
+{
+  template<typename Index, typename Value, typename Func, typename Reduction>
+    __forceinline Value sequential_reduce( const Index first, const Index last, const Value& identity, const Func& func, const Reduction& reduction ) 
+  {
+    return func(range<Index>(first,last));
+  }
+
+  template<typename Index, typename Value, typename Func, typename Reduction>
+    __forceinline Value sequential_reduce( const Index first, const Index last, const Index minStepSize, const Value& identity, const Func& func, const Reduction& reduction )
+  {
+    return func(range<Index>(first,last));
+  }
+
+  template<typename Index, typename Value, typename Func, typename Reduction>
+    __noinline Value parallel_reduce_internal( Index taskCount, const Index first, const Index last, const Index minStepSize, const Value& identity, const Func& func, const Reduction& reduction )
+  {
+    const Index maxTasks = 512;
+    const Index threadCount = (Index) TaskScheduler::threadCount();
+    taskCount = min(taskCount,threadCount,maxTasks);
+
+    /* parallel invocation of all tasks */
+    dynamic_large_stack_array(Value,values,taskCount,8192); // consumes at most 8192 bytes on the stack
+    parallel_for(taskCount, [&](const Index taskIndex) {
+        const Index k0 = first+(taskIndex+0)*(last-first)/taskCount;
+        const Index k1 = first+(taskIndex+1)*(last-first)/taskCount;
+        values[taskIndex] = func(range<Index>(k0,k1));
+      });
+
+    /* perform reduction over all tasks */
+    Value v = identity;
+    for (Index i=0; i<taskCount; i++) v = reduction(v,values[i]);
+    return v;
+  }
+
+  template<typename Index, typename Value, typename Func, typename Reduction>
+    __forceinline Value parallel_reduce( const Index first, const Index last, const Index minStepSize, const Value& identity, const Func& func, const Reduction& reduction )
+  {
+#if defined(TASKING_INTERNAL) && !defined(TASKING_TBB)
+
+    /* fast path for small number of iterations */
+    Index taskCount = (last-first+minStepSize-1)/minStepSize;
+    if (likely(taskCount == 1)) {
+      return func(range<Index>(first,last));
+    }
+    return parallel_reduce_internal(taskCount,first,last,minStepSize,identity,func,reduction);
+
+#elif defined(TASKING_TBB)
+  #if TBB_INTERFACE_VERSION >= 12002
+    tbb::task_group_context context;
+    const Value v = tbb::parallel_reduce(tbb::blocked_range<Index>(first,last,minStepSize),identity,
+      [&](const tbb::blocked_range<Index>& r, const Value& start) { return reduction(start,func(range<Index>(r.begin(),r.end()))); },
+      reduction,context);
+    //if (context.is_group_execution_cancelled())
+    //  throw std::runtime_error("task cancelled");
+    return v;
+  #else
+    const Value v = tbb::parallel_reduce(tbb::blocked_range<Index>(first,last,minStepSize),identity,
+      [&](const tbb::blocked_range<Index>& r, const Value& start) { return reduction(start,func(range<Index>(r.begin(),r.end()))); },
+      reduction);
+    //if (tbb::task::self().is_cancelled())
+    //  throw std::runtime_error("task cancelled");
+    return v;
+  #endif
+#else // TASKING_PPL
+    struct AlignedValue
+    {
+      char storage[__alignof(Value)+sizeof(Value)];
+      static uintptr_t alignUp(uintptr_t p, size_t a) { return p + (~(p - 1) % a); };
+      Value* getValuePtr() { return reinterpret_cast<Value*>(alignUp(uintptr_t(storage), __alignof(Value))); }
+      const Value* getValuePtr() const { return reinterpret_cast<Value*>(alignUp(uintptr_t(storage), __alignof(Value))); }
+      AlignedValue(const Value& v) { new(getValuePtr()) Value(v); }
+      AlignedValue(const AlignedValue& v) { new(getValuePtr()) Value(*v.getValuePtr()); }
+      AlignedValue(const AlignedValue&& v) { new(getValuePtr()) Value(*v.getValuePtr()); };
+      AlignedValue& operator = (const AlignedValue& v) { *getValuePtr() = *v.getValuePtr(); return *this; };
+      AlignedValue& operator = (const AlignedValue&& v) { *getValuePtr() = *v.getValuePtr(); return *this; };
+      operator Value() const { return *getValuePtr(); }
+    };
+    
+    struct Iterator_Index
+    {
+      Index v;
+      typedef std::forward_iterator_tag iterator_category;
+      typedef AlignedValue value_type;
+      typedef Index difference_type;
+      typedef Index distance_type;
+      typedef AlignedValue* pointer;
+      typedef AlignedValue& reference;
+      __forceinline Iterator_Index() {}
+      __forceinline Iterator_Index(Index v) : v(v) {}
+      __forceinline bool operator== (Iterator_Index other) { return v == other.v; }
+      __forceinline bool operator!= (Iterator_Index other) { return v != other.v; }
+      __forceinline Iterator_Index operator++() { return Iterator_Index(++v); }
+      __forceinline Iterator_Index operator++(int) { return Iterator_Index(v++); }
+    };
+    
+    auto range_reduction = [&](Iterator_Index begin, Iterator_Index end, const AlignedValue& start) {
+      assert(begin.v < end.v);
+      return reduction(start, func(range<Index>(begin.v, end.v)));
+    };
+    const Value v = concurrency::parallel_reduce(Iterator_Index(first), Iterator_Index(last), AlignedValue(identity), range_reduction, reduction);
+    return v;
+#endif
+  }
+
+  template<typename Index, typename Value, typename Func, typename Reduction>
+    __forceinline Value parallel_reduce( const Index first, const Index last, const Index minStepSize, const Index parallel_threshold, const Value& identity, const Func& func, const Reduction& reduction )
+  {
+    if (likely(last-first < parallel_threshold)) {
+      return func(range<Index>(first,last)); 
+    } else {
+      return parallel_reduce(first,last,minStepSize,identity,func,reduction);
+    }
+  }
+
+  template<typename Index, typename Value, typename Func, typename Reduction>
+    __forceinline Value parallel_reduce( const range<Index> range, const Index minStepSize, const Index parallel_threshold, const Value& identity, const Func& func, const Reduction& reduction ) 
+  {
+    return parallel_reduce(range.begin(),range.end(),minStepSize,parallel_threshold,identity,func,reduction);
+  }
+
+  template<typename Index, typename Value, typename Func, typename Reduction>
+    __forceinline Value parallel_reduce( const Index first, const Index last, const Value& identity, const Func& func, const Reduction& reduction )
+  {
+    auto funcr = [&] ( const range<Index> r ) {
+      Value v = identity;
+      for (Index i=r.begin(); i<r.end(); i++)
+        v = reduction(v,func(i));
+      return v;
+    };
+    return parallel_reduce(first,last,Index(1),identity,funcr,reduction);
+  }
+
+  template<typename Index, typename Value, typename Func, typename Reduction>
+    __forceinline Value parallel_reduce( const range<Index> range, const Value& identity, const Func& func, const Reduction& reduction )
+  {
+    return parallel_reduce(range.begin(),range.end(),Index(1),identity,func,reduction);
+  }
+}