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/*
* Copyright 2020 Patrick Stotko
* 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 <iostream>
#include <thrust/copy.h>
#include <thrust/reduce.h>
#include <thrust/sequence.h>
#include <stdgpu/iterator.h> // device_begin, device_end
#include <stdgpu/memory.h> // createDeviceArray, destroyDeviceArray
#include <stdgpu/platform.h> // STDGPU_HOST_DEVICE
#include <stdgpu/vector.cuh> // stdgpu::vector
void
insert_neighbors_with_duplicates(const int* d_input, const stdgpu::index_t n, stdgpu::vector<int>& vec)
{
#pragma omp parallel for
for (stdgpu::index_t i = 0; i < n; ++i)
{
int num = d_input[i];
int num_neighborhood[3] = { num - 1, num, num + 1 };
for (int num_neighbor : num_neighborhood)
{
vec.push_back(num_neighbor);
}
}
}
int
main()
{
//
// EXAMPLE DESCRIPTION
// -------------------
// This example demonstrates how stdgpu::vector is used to compute a set of duplicated numbers.
// Every number is contained 3 times, except for the first and last one which is contained only 2 times.
//
const stdgpu::index_t n = 100;
int* d_input = createDeviceArray<int>(n);
stdgpu::vector<int> vec = stdgpu::vector<int>::createDeviceObject(3 * n);
thrust::sequence(stdgpu::device_begin(d_input), stdgpu::device_end(d_input), 1);
// d_input : 1, 2, 3, ..., 100
insert_neighbors_with_duplicates(d_input, n, vec);
// vec : 0, 1, 1, 2, 2, 2, 3, 3, 3, ..., 99, 99, 99, 100, 100, 101
auto range_vec = vec.device_range();
int sum = thrust::reduce(range_vec.begin(), range_vec.end(), 0, thrust::plus<int>());
const int sum_closed_form = 3 * (n * (n + 1) / 2);
std::cout << "The set of duplicated numbers contains " << vec.size() << " elements (" << 3 * n
<< " expected) and the computed sum is " << sum << " (" << sum_closed_form << " expected)" << std::endl;
destroyDeviceArray<int>(d_input);
stdgpu::vector<int>::destroyDeviceObject(vec);
}
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