60 lines
2.5 KiB
C++
Executable File
60 lines
2.5 KiB
C++
Executable File
// ======================================================================== //
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// Copyright 2009-2014 Intel Corporation //
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// //
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// Licensed under the Apache License, Version 2.0 (the "License"); //
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// you may not use this file except in compliance with the License. //
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// You may obtain a copy of the License at //
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// //
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// http://www.apache.org/licenses/LICENSE-2.0 //
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// //
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// Unless required by applicable law or agreed to in writing, software //
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// distributed under the License is distributed on an "AS IS" BASIS, //
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. //
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// See the License for the specific language governing permissions and //
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// limitations under the License. //
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// ======================================================================== //
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#pragma once
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#include "parallel_for.h"
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namespace embree
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{
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template<typename Value>
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struct ParallelPrefixSumState
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{
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enum { MAX_TASKS = 32 };
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Value counts[MAX_TASKS];
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Value sums [MAX_TASKS];
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};
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template<typename Index, typename Value, typename Func, typename Reduction>
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__forceinline Value parallel_prefix_sum( ParallelPrefixSumState<Value>& state, Index first, Index last, Index minStepSize, const Value& identity, const Func& func, const Reduction& reduction)
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{
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/* calculate number of tasks to use */
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LockStepTaskScheduler* scheduler = LockStepTaskScheduler::instance();
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const size_t numThreads = scheduler->getNumThreads();
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const size_t numBlocks = (last-first+minStepSize-1)/minStepSize;
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const size_t taskCount = min(numThreads,numBlocks,size_t(ParallelPrefixSumState<Value>::MAX_TASKS));
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/* perform parallel prefix sum */
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parallel_for(taskCount, [&](const size_t taskIndex)
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{
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const size_t i0 = first+(taskIndex+0)*(last-first)/taskCount;
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const size_t i1 = first+(taskIndex+1)*(last-first)/taskCount;
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state.counts[taskIndex] = func(range<size_t>(i0,i1),state.sums[taskIndex]);
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});
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/* calculate prefix sum */
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Value sum=0;
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for (size_t i=0; i<taskCount; i++)
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{
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const Value c = state.counts[i];
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state.sums[i] = sum;
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sum=reduction(sum,c);
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}
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return sum;
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}
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}
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