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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/reduce.h>
#include <thrust/sequence.h>
#include <thrust/transform.h>
#include <stdgpu/iterator.h> // device_begin, device_end
#include <stdgpu/memory.h> // createDeviceArray, destroyDeviceArray
#include <stdgpu/platform.h> // STDGPU_HOST_DEVICE
#include <stdgpu/ranges.h> // device_range
#include <stdgpu/unordered_set.cuh> // stdgpu::unordered_set
struct square_int
{
STDGPU_HOST_DEVICE int
operator()(const int x) const
{
return x * x;
}
};
int
main()
{
//
// EXAMPLE DESCRIPTION
// -------------------
// This example demonstrates the usage of ranges with thrust at the example of stdgpu::unordered_set.
// Furthermore, it outlines how they would be used if thrust had a proper range interface.
//
const stdgpu::index_t n = 100;
int* d_input = createDeviceArray<int>(n);
int* d_result = createDeviceArray<int>(n);
stdgpu::unordered_set<int> set = stdgpu::unordered_set<int>::createDeviceObject(n);
thrust::sequence(stdgpu::device_begin(d_input), stdgpu::device_end(d_input), 1);
// d_input : 1, 2, 3, ..., 100
auto range_int = stdgpu::device_range<int>(d_input);
thrust::transform(range_int.begin(), range_int.end(), stdgpu::device_begin(d_result), square_int());
// If thrust had a range interface (maybe in a future release), the above call could also be written in a shorter
// form:
//
// thrust::transform(stdgpu::device_range<int>(d_input),
// stdgpu::device_begin(d_result),
// square_int());
// d_result : 1, 4, 9, ..., 10000
set.insert(stdgpu::device_cbegin(d_result), stdgpu::device_cend(d_result));
// set : 1, 4, 9, ..., 10000
auto range_set = set.device_range();
int sum = thrust::reduce(range_set.begin(), range_set.end(), 0, thrust::plus<int>());
// If thrust had a range interface (maybe in a future release), the above call could also be written in a shorter
// form:
//
// int sum = thrust::reduce(set.device_range(),
// 0,
// thrust::plus<int>());
//
// Or the call to device_range may also become an implicit operation in the future.
const int sum_closed_form = n * (n + 1) * (2 * n + 1) / 6;
std::cout << "The computed sum from i = 1 to " << n << " of i^2 is " << sum << " (" << sum_closed_form
<< " expected)" << std::endl;
destroyDeviceArray<int>(d_input);
destroyDeviceArray<int>(d_result);
stdgpu::unordered_set<int>::destroyDeviceObject(set);
}
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