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file_after.cpp
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file_after.cpp
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#if 0
set -ex
nvc++ -std=c++20 -stdpar=gpu -gpu=nomanaged -o file_after $0
./file_after 10
exit 0
#endif
/*
* SPDX-FileCopyrightText: Copyright (c) 2023 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
* SPDX-License-Identifier: MIT
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include <algorithm>
#include <execution>
#include <fcntl.h>
#include <fstream>
#include <functional>
#include <iostream>
#include <ranges>
#include <span>
#include <stdio.h>
#include <sys/mman.h>
#include <vector>
void use_data(std::span<char>);
void sortfile(int fd, int N) {
char* buffer = (char*)mmap(NULL, N, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
if (buffer == nullptr) {
std::cerr << "Failed to mmap file!" << std::endl;
abort();
}
std::sort(std::execution::par, buffer, buffer + N, std::greater{});
use_data(std::span{buffer, N});
munmap(buffer, N);
}
void use_data(std::span<char> data) {
for (auto c : data) std::cout << c << std::endl;
}
int main(int argc, char* argv[]) {
if (argc != 2) {
std::cerr << "ERROR: missing length argument" << std::endl;
std::cerr << "Usage: " << argv[0] << " <file bytes> " << std::endl;
abort();
}
std::size_t N = std::stoll(argv[1]);
// Generate a file with n elements
char const* fname = "file_after.txt";
{
std::cout << "Generating file with " << N << " bytes..." << std::endl;
std::ofstream out(fname);
if (!out) {
std::cerr << "File open failed!" << std::endl;
abort();
}
std::vector<unsigned char> buffer(N);
std::for_each_n(std::execution::par, std::views::iota(0).begin(), N,
[&](int i) { buffer[i] = (unsigned char)'0' + (unsigned char)i; });
out.write((const char*)buffer.data(), N);
out.close();
}
int fd = open(fname, O_RDWR);
if (fd == -1) {
std::cerr << "Failed to read file" << std::endl;
abort();
}
sortfile(fd, N);
return 0;
}