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/*
* Copyright 2019 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/sequence.h>
#include <stdgpu/atomic.cuh> // stdgpu::atomic
#include <stdgpu/bitset.cuh> // stdgpu::bitset
#include <stdgpu/iterator.h> // device_begin, device_end
#include <stdgpu/memory.h> // createDeviceArray, destroyDeviceArray
#include <stdgpu/platform.h> // STDGPU_HOST_DEVICE
struct is_odd
{
STDGPU_HOST_DEVICE bool
operator()(const int x) const
{
return x % 2 == 1;
}
};
void
set_bits(const int* d_result, const stdgpu::index_t d_result_size, stdgpu::bitset<>& bits, stdgpu::atomic<int>& counter)
{
#pragma omp parallel for
for (stdgpu::index_t i = 0; i < d_result_size; ++i)
{
bool was_set = bits.set(d_result[i]);
if (!was_set)
{
++counter;
}
}
}
int
main()
{
//
// EXAMPLE DESCRIPTION
// -------------------
// This example shows how every second bit of stdgpu::bitset can be set concurrently in a GPU kernel.
//
const stdgpu::index_t n = 100;
int* d_input = createDeviceArray<int>(n);
int* d_result = createDeviceArray<int>(n / 2);
stdgpu::bitset<> bits = stdgpu::bitset<>::createDeviceObject(n);
stdgpu::atomic<int> counter = stdgpu::atomic<int>::createDeviceObject();
thrust::sequence(stdgpu::device_begin(d_input), stdgpu::device_end(d_input), 1);
// d_input : 1, 2, 3, ..., 100
thrust::copy_if(stdgpu::device_cbegin(d_input),
stdgpu::device_cend(d_input),
stdgpu::device_begin(d_result),
is_odd());
// d_result : 1, 3, 5, ..., 99
// bits : 000000..00
counter.store(0);
set_bits(d_result, n / 2, bits, counter);
// bits : 010101...01
std::cout << "First run: The number of set bits is " << bits.count() << " (" << n / 2 << " expected; "
<< counter.load() << " of those previously unset)" << std::endl;
counter.store(0);
set_bits(d_result, n / 2, bits, counter);
// bits : 010101...01
std::cout << "Second run: The number of set bits is " << bits.count() << " (" << n / 2 << " expected; "
<< counter.load() << " of those previously unset)" << std::endl;
destroyDeviceArray<int>(d_input);
destroyDeviceArray<int>(d_result);
stdgpu::bitset<>::destroyDeviceObject(bits);
stdgpu::atomic<int>::destroyDeviceObject(counter);
}
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