godot/thirdparty/embree/common/algorithms/parallel_prefix_sum.cpp

// Copyright 2009-2020 Intel Corporation
// SPDX-License-Identifier: Apache-2.0

#include "parallel_prefix_sum.h"
#include "../sys/regression.h"

namespace embree
{
  struct parallel_prefix_sum_regression_test : public RegressionTest
  {
    parallel_prefix_sum_regression_test(const char* name) : RegressionTest(name) {
      registerRegressionTest(this);
    }
    
    bool run ()
    {
      bool passed = true;
      const size_t M = 10;
      
      for (size_t N=10; N<10000000; N=size_t(2.1*N))
      {
	/* initialize array with random numbers */
        uint32_t sum0 = 0;
	std::vector<uint32_t> src(N);
	for (size_t i=0; i<N; i++) {
	  sum0 += src[i] = rand();
        }
        
	/* calculate parallel prefix sum */
	std::vector<uint32_t> dst(N);
	for (auto& v : dst) v = 0;
	
	for (size_t i=0; i<M; i++) {
	  uint32_t sum1 = parallel_prefix_sum(src,dst,N,0,std::plus<uint32_t>());
          passed &= (sum0 == sum1);
        }
        
	/* check if prefix sum is correct */
	for (size_t i=0, sum=0; i<N; sum+=src[i++])
	  passed &= ((uint32_t)sum == dst[i]);
      }
      
      return passed;
    }
  };

  parallel_prefix_sum_regression_test parallel_prefix_sum_regression("parallel_prefix_sum_regression");
}