1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
|
/*
* 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/for_each.h>
#include <thrust/sequence.h>
#include <thrust/transform.h>
#include <stdgpu/atomic.cuh> // stdgpu::atomic
#include <stdgpu/iterator.h> // device_begin, device_end
#include <stdgpu/memory.h> // createDeviceArray, destroyDeviceArray
#include <stdgpu/platform.h> // STDGPU_HOST_DEVICE
struct square_int
{
STDGPU_HOST_DEVICE int
operator()(const int x) const
{
return x * x;
}
};
class atomic_add
{
public:
explicit atomic_add(const stdgpu::atomic<int>& sum)
: _sum(sum)
{
}
STDGPU_DEVICE_ONLY void
operator()(const int x)
{
_sum.fetch_add(x);
}
private:
stdgpu::atomic<int> _sum;
};
int
main()
{
//
// EXAMPLE DESCRIPTION
// -------------------
// This example demonstrates how stdgpu::atomic can be used to compute a sum of numbers by atomic addition.
//
const stdgpu::index_t n = 100;
int* d_input = createDeviceArray<int>(n);
int* d_result = createDeviceArray<int>(n);
stdgpu::atomic<int> sum = stdgpu::atomic<int>::createDeviceObject();
thrust::sequence(stdgpu::device_begin(d_input), stdgpu::device_end(d_input), 1);
// d_input : 1, 2, 3, ..., 100
thrust::transform(stdgpu::device_cbegin(d_input),
stdgpu::device_cend(d_input),
stdgpu::device_begin(d_result),
square_int());
// d_result : 1, 4, 9, ..., 10000
sum.store(0);
thrust::for_each(stdgpu::device_cbegin(d_result), stdgpu::device_cend(d_result), atomic_add(sum));
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.load() << " (" << sum_closed_form
<< " expected)" << std::endl;
destroyDeviceArray<int>(d_input);
destroyDeviceArray<int>(d_result);
stdgpu::atomic<int>::destroyDeviceObject(sum);
}
|
