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thread_count.h
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1 /*
2  * Copyright 2019 OmniSci, Inc.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef THREAD_COUNT_H
18 #define THREAD_COUNT_H
19 
20 #include <unistd.h>
21 #include <algorithm>
22 
23 extern std::size_t g_cpu_threads_override;
24 
25 inline int cpu_threads() {
26  // could use std::thread::hardware_concurrency(), but some
27  // slightly out-of-date compilers (gcc 4.7) implement it as always 0.
28  // Play it POSIX.1 safe instead.
29  auto ov = g_cpu_threads_override;
30  return (ov <= 0) ? std::max(2 * sysconf(_SC_NPROCESSORS_CONF), 1L) : ov;
31 }
32 
33 #endif // THREAD_COUNT_H
std::size_t g_cpu_threads_override
int cpu_threads()
Definition: thread_count.h:25