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/*
* Adapted from code copyright 2009-2010 NVIDIA Corporation
* Modifications Copyright 2011, Blender Foundation.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "bvh/bvh_sort.h"
#include "bvh/bvh_build.h"
#include "util/util_algorithm.h"
#include "util/util_task.h"
CCL_NAMESPACE_BEGIN
static const int BVH_SORT_THRESHOLD = 4096;
struct BVHReferenceCompare {
public:
int dim;
const BVHUnaligned *unaligned_heuristic;
const Transform *aligned_space;
BVHReferenceCompare(int dim,
const BVHUnaligned *unaligned_heuristic,
const Transform *aligned_space)
: dim(dim), unaligned_heuristic(unaligned_heuristic), aligned_space(aligned_space)
{
}
__forceinline BoundBox get_prim_bounds(const BVHReference &prim) const
{
return (aligned_space != NULL) ?
unaligned_heuristic->compute_aligned_prim_boundbox(prim, *aligned_space) :
prim.bounds();
}
/* Compare two references.
*
* Returns value is similar to return value of strcmp().
*/
__forceinline int compare(const BVHReference &ra, const BVHReference &rb) const
{
BoundBox ra_bounds = get_prim_bounds(ra), rb_bounds = get_prim_bounds(rb);
float ca = ra_bounds.min[dim] + ra_bounds.max[dim];
float cb = rb_bounds.min[dim] + rb_bounds.max[dim];
if (ca < cb)
return -1;
else if (ca > cb)
return 1;
else if (ra.prim_object() < rb.prim_object())
return -1;
else if (ra.prim_object() > rb.prim_object())
return 1;
else if (ra.prim_index() < rb.prim_index())
return -1;
else if (ra.prim_index() > rb.prim_index())
return 1;
else if (ra.prim_type() < rb.prim_type())
return -1;
else if (ra.prim_type() > rb.prim_type())
return 1;
return 0;
}
bool operator()(const BVHReference &ra, const BVHReference &rb)
{
return (compare(ra, rb) < 0);
}
};
static void bvh_reference_sort_threaded(TaskPool *task_pool,
BVHReference *data,
const int job_start,
const int job_end,
const BVHReferenceCompare &compare);
/* Multi-threaded reference sort. */
static void bvh_reference_sort_threaded(TaskPool *task_pool,
BVHReference *data,
const int job_start,
const int job_end,
const BVHReferenceCompare &compare)
{
int start = job_start, end = job_end;
bool have_work = (start < end);
while (have_work) {
const int count = job_end - job_start;
if (count < BVH_SORT_THRESHOLD) {
/* Number of reference low enough, faster to finish the job
* in one thread rather than to spawn more threads.
*/
sort(data + job_start, data + job_end + 1, compare);
break;
}
/* Single QSort step.
* Use median-of-three method for the pivot point.
*/
int left = start, right = end;
int center = (left + right) >> 1;
if (compare.compare(data[left], data[center]) > 0) {
swap(data[left], data[center]);
}
if (compare.compare(data[left], data[right]) > 0) {
swap(data[left], data[right]);
}
if (compare.compare(data[center], data[right]) > 0) {
swap(data[center], data[right]);
}
swap(data[center], data[right - 1]);
BVHReference median = data[right - 1];
do {
while (compare.compare(data[left], median) < 0) {
++left;
}
while (compare.compare(data[right], median) > 0) {
--right;
}
if (left <= right) {
swap(data[left], data[right]);
++left;
--right;
}
} while (left <= right);
/* We only create one new task here to reduce downside effects of
* latency in TaskScheduler.
* So generally current thread keeps working on the left part of the
* array, and we create new task for the right side.
* However, if there's nothing to be done in the left side of the array
* we don't create any tasks and make it so current thread works on the
* right side.
*/
have_work = false;
if (left < end) {
if (start < right) {
task_pool->push(
function_bind(bvh_reference_sort_threaded, task_pool, data, left, end, compare), true);
}
else {
start = left;
have_work = true;
}
}
if (start < right) {
end = right;
have_work = true;
}
}
}
void bvh_reference_sort(int start,
int end,
BVHReference *data,
int dim,
const BVHUnaligned *unaligned_heuristic,
const Transform *aligned_space)
{
const int count = end - start;
BVHReferenceCompare compare(dim, unaligned_heuristic, aligned_space);
if (count < BVH_SORT_THRESHOLD) {
/* It is important to not use any mutex if array is small enough,
* otherwise we end up in situation when we're going to sleep far
* too often.
*/
sort(data + start, data + end, compare);
}
else {
TaskPool task_pool;
bvh_reference_sort_threaded(&task_pool, data, start, end - 1, compare);
task_pool.wait_work();
}
}
CCL_NAMESPACE_END
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