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project_6/cccl_upstream/thrust/examples/weld_vertices.cu
EngineX CI 56fd68e7dd [INFRA] Import NVIDIA/CCCL upstream as optimization reference library
CCCL (CUDA C++ Core Libraries) provides:
- CUB: device/block/warp-level GPU primitives (reduce, scan, sort, topk)
- Thrust: high-level parallel algorithms (transform_reduce, sort, scan)
- libcudacxx: CUDA C++ standard library (atomics, barriers, memory)
- cudax: experimental features (memory resources, allocators)
- Tuning policies: per-SM hardware-specific algorithm parameters

Competition optimization vectors mapped to CCCL:
- Output TPS (83% weight): warp_reduce, block_reduce, device_topk
- Input TPS (14% weight): device_scan, block_load, prefetch
- Cache TPS (3% weight): prefix caching strategy patterns
- Memory (0.9 util): pooled/cached/buddy allocators

Source: https://github.com/NVIDIA/cccl (shallow clone, HEAD only)
License: Apache-2.0
2026-07-30 09:35:51 +00:00

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#include <thrust/binary_search.h>
#include <thrust/device_vector.h>
#include <thrust/host_vector.h>
#include <thrust/remove.h>
#include <thrust/sort.h>
#include <thrust/unique.h>
#include <iostream>
/*
* This example "welds" triangle vertices together by taking as
* input "triangle soup" and eliminating redundant vertex positions
* and shared edges. A connected mesh is the result.
*
*
* Input: 9 vertices representing a mesh with 3 triangles
*
* Mesh Vertices
* ------ (2) (5)--(4) (8)
* | \ 2| \ | \ \ | | \
* | \ | \ <-> | \ \ | | \
* | 0 \| 1 \ | \ \ | | \
* ----------- (0)--(1) (3) (6)--(7)
*
* (vertex 1 equals vertex 3, vertex 2 equals vertex 5, ...)
*
* Output: mesh representation with 5 vertices and 9 indices
*
* Vertices Indices
* (1)--(3) [(0,2,1),
* | \ | \ (2,3,1),
* | \ | \ (2,4,3)]
* | \| \
* (0)--(2)--(4)
*/
// define a 2d float vector
using vec2 = cuda::std::tuple<float, float>;
int main()
{
// allocate memory for input mesh representation
thrust::device_vector<vec2> input(9);
thrust::host_vector<vec2> h_input{
vec2(0, 0),
vec2(1, 0),
vec2(0, 1), // First Triangle
vec2(1, 0),
vec2(1, 1),
vec2(0, 1), // Second Triangle
vec2(1, 0),
vec2(2, 0),
vec2(1, 1) // Third Triangle
};
input = h_input;
// allocate space for output mesh representation
thrust::device_vector<vec2> vertices = input;
thrust::device_vector<unsigned int> indices(input.size());
// sort vertices to bring duplicates together
thrust::sort(vertices.begin(), vertices.end());
// find unique vertices and erase redundancies
vertices.erase(thrust::unique(vertices.begin(), vertices.end()), vertices.end());
// find index of each input vertex in the list of unique vertices
thrust::lower_bound(vertices.begin(), vertices.end(), input.begin(), input.end(), indices.begin());
// print output mesh representation
std::cout << "Output Representation" << '\n';
for (size_t i = 0; i < vertices.size(); i++)
{
vec2 v = vertices[i];
std::cout << " vertices[" << i << "] = (" << cuda::std::get<0>(v) << "," << cuda::std::get<1>(v) << ")" << '\n';
}
for (size_t i = 0; i < indices.size(); i++)
{
std::cout << " indices[" << i << "] = " << indices[i] << '\n';
}
return 0;
}