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// Copyright 2009 Intel Corporation
// SPDX-License-Identifier: Apache-2.0
#include "Distribution1D.ih"
#ifdef OSPRAY_TARGET_SYCL
#include <limits>
#endif
// Pre-condition: size > 0
OSPRAY_BEGIN_ISPC_NAMESPACE
SYCL_EXTERNAL export uniform float Distribution1D_create(
const uniform int size, uniform float *uniform cdf)
{
// accumulate the function
// using varying float and exclusive_scan_add(float v) is much slower
uniform float sum = cdf[0];
for (uniform int i = 1; i < size; i++)
cdf[i] = sum += cdf[i];
// compute reciprocal sum
const uniform float rcpSum = 1.0f / sum;
// next representable number in float greater than 1.0f
const uniform float nextAfter1 = 0x1.000002p+0f;
// normalize
#ifdef OSPRAY_TARGET_SYCL
for (int i = 0; i < size; ++i) {
#else
foreach (i = 0 ... size) {
#endif
const float c = cdf[i];
// handle cornercases (sum=0 -> rcpSum=inf; correct termination of sampling
// with s=1.0f)
const float q = c >= sum ? nextAfter1 : c * rcpSum;
cdf[i] = q;
}
return sum;
}
OSPRAY_END_ISPC_NAMESPACE
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