crates/num_cpus/src/lib.rs - platform/external/rust/android-crates-io - Git at Google

 //! A crate with utilities to determine the number of CPUs available on the
 //! current system.
 //!
 //! Sometimes the CPU will exaggerate the number of CPUs it contains, because it can use
 //! [processor tricks] to deliver increased performance when there are more threads. This
 //! crate provides methods to get both the logical and physical numbers of cores.
 //!
 //! This information can be used as a guide to how many tasks can be run in parallel.
 //! There are many properties of the system architecture that will affect parallelism,
 //! for example memory access speeds (for all the caches and RAM) and the physical
 //! architecture of the processor, so the number of CPUs should be used as a rough guide
 //! only.
 //!
 //!
 //! ## Examples
 //!
 //! Fetch the number of logical CPUs.
 //!
 //! ```
 //! let cpus = num_cpus::get();
 //! ```
 //!
 //! See [`rayon::Threadpool`] for an example of where the number of CPUs could be
 //! used when setting up parallel jobs (Where the threadpool example uses a fixed
 //! number 8, it could use the number of CPUs).
 //!
 //! [processor tricks]: https://en.wikipedia.org/wiki/Simultaneous_multithreading
 //! [`rayon::ThreadPool`]: https://docs.rs/rayon/1.*/rayon/struct.ThreadPool.html
 #![cfg_attr(test, deny(warnings))]
 #![deny(missing_docs)]
 #![allow(non_snake_case)]

 #[cfg(not(windows))]
 extern crate libc;

 #[cfg(target_os = "hermit")]
 extern crate hermit_abi;

 #[cfg(target_os = "linux")]
 mod linux;
 #[cfg(target_os = "linux")]
 use linux::{get_num_cpus, get_num_physical_cpus};

 /// Returns the number of available CPUs of the current system.
 ///
 /// This function will get the number of logical cores. Sometimes this is different from the number
 /// of physical cores (See [Simultaneous multithreading on Wikipedia][smt]).
 ///
 /// This will always return at least `1`.
 ///
 /// # Examples
 ///
 /// ```
 /// let cpus = num_cpus::get();
 /// if cpus > 1 {
 ///     println!("We are on a multicore system with {} CPUs", cpus);
 /// } else {
 ///     println!("We are on a single core system");
 /// }
 /// ```
 ///
 /// # Note
 ///
 /// This will check [sched affinity] on Linux, showing a lower number of CPUs if the current
 /// thread does not have access to all the computer's CPUs.
 ///
 /// This will also check [cgroups], frequently used in containers to constrain CPU usage.
 ///
 /// [smt]: https://en.wikipedia.org/wiki/Simultaneous_multithreading
 /// [sched affinity]: http://www.gnu.org/software/libc/manual/html_node/CPU-Affinity.html
 /// [cgroups]: https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
 #[inline]
 pub fn get() -> usize {
     get_num_cpus()
 }

 /// Returns the number of physical cores of the current system.
 ///
 /// This will always return at least `1`.
 ///
 /// # Note
 ///
 /// Physical count is supported only on Linux, mac OS and Windows platforms.
 /// On other platforms, or if the physical count fails on supported platforms,
 /// this function returns the same as [`get()`], which is the number of logical
 /// CPUS.
 ///
 /// # Examples
 ///
 /// ```
 /// let logical_cpus = num_cpus::get();
 /// let physical_cpus = num_cpus::get_physical();
 /// if logical_cpus > physical_cpus {
 ///     println!("We have simultaneous multithreading with about {:.2} \
 ///               logical cores to 1 physical core.",
 ///               (logical_cpus as f64) / (physical_cpus as f64));
 /// } else if logical_cpus == physical_cpus {
 ///     println!("Either we don't have simultaneous multithreading, or our \
 ///               system doesn't support getting the number of physical CPUs.");
 /// } else {
 ///     println!("We have less logical CPUs than physical CPUs, maybe we only have access to \
 ///               some of the CPUs on our system.");
 /// }
 /// ```
 ///
 /// [`get()`]: fn.get.html
 #[inline]
 pub fn get_physical() -> usize {
     get_num_physical_cpus()
 }


 #[cfg(not(any(
     target_os = "linux",
     target_os = "windows",
     target_os = "macos",
     target_os = "openbsd",
     target_os = "aix")))]
 #[inline]
 fn get_num_physical_cpus() -> usize {
     // Not implemented, fall back
     get_num_cpus()
 }

 #[cfg(target_os = "windows")]
 fn get_num_physical_cpus() -> usize {
     match get_num_physical_cpus_windows() {
         Some(num) => num,
         None => get_num_cpus()
     }
 }

 #[cfg(target_os = "windows")]
 fn get_num_physical_cpus_windows() -> Option<usize> {
     // Inspired by https://msdn.microsoft.com/en-us/library/ms683194

     use std::ptr;
     use std::mem;

     #[allow(non_upper_case_globals)]
     const RelationProcessorCore: u32 = 0;

     #[repr(C)]
     #[allow(non_camel_case_types)]
     struct SYSTEM_LOGICAL_PROCESSOR_INFORMATION {
         mask: usize,
         relationship: u32,
         _unused: [u64; 2]
     }

     extern "system" {
         fn GetLogicalProcessorInformation(
             info: *mut SYSTEM_LOGICAL_PROCESSOR_INFORMATION,
             length: &mut u32
         ) -> u32;
     }

     // First we need to determine how much space to reserve.

     // The required size of the buffer, in bytes.
     let mut needed_size = 0;

     unsafe {
         GetLogicalProcessorInformation(ptr::null_mut(), &mut needed_size);
     }

     let struct_size = mem::size_of::<SYSTEM_LOGICAL_PROCESSOR_INFORMATION>() as u32;

     // Could be 0, or some other bogus size.
     if needed_size == 0 || needed_size < struct_size || needed_size % struct_size != 0 {
         return None;
     }

     let count = needed_size / struct_size;

     // Allocate some memory where we will store the processor info.
     let mut buf = Vec::with_capacity(count as usize);

     let result;

     unsafe {
         result = GetLogicalProcessorInformation(buf.as_mut_ptr(), &mut needed_size);
     }

     // Failed for any reason.
     if result == 0 {
         return None;
     }

     let count = needed_size / struct_size;

     unsafe {
         buf.set_len(count as usize);
     }

     let phys_proc_count = buf.iter()
         // Only interested in processor packages (physical processors.)
         .filter(|proc_info| proc_info.relationship == RelationProcessorCore)
         .count();

     if phys_proc_count == 0 {
         None
     } else {
         Some(phys_proc_count)
     }
 }

 #[cfg(windows)]
 fn get_num_cpus() -> usize {
     #[repr(C)]
     struct SYSTEM_INFO {
         wProcessorArchitecture: u16,
         wReserved: u16,
         dwPageSize: u32,
         lpMinimumApplicationAddress: *mut u8,
         lpMaximumApplicationAddress: *mut u8,
         dwActiveProcessorMask: *mut u8,
         dwNumberOfProcessors: u32,
         dwProcessorType: u32,
         dwAllocationGranularity: u32,
         wProcessorLevel: u16,
         wProcessorRevision: u16,
     }

     extern "system" {
         fn GetSystemInfo(lpSystemInfo: *mut SYSTEM_INFO);
     }

     unsafe {
         let mut sysinfo: SYSTEM_INFO = std::mem::zeroed();
         GetSystemInfo(&mut sysinfo);
         sysinfo.dwNumberOfProcessors as usize
     }
 }

 #[cfg(any(target_os = "freebsd",
           target_os = "dragonfly",
           target_os = "netbsd"))]
 fn get_num_cpus() -> usize {
     use std::ptr;

     let mut cpus: libc::c_uint = 0;
     let mut cpus_size = std::mem::size_of_val(&cpus);

     unsafe {
         cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint;
     }
     if cpus < 1 {
         let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
         unsafe {
             libc::sysctl(mib.as_mut_ptr(),
                          2,
                          &mut cpus as *mut _ as *mut _,
                          &mut cpus_size as *mut _ as *mut _,
                          ptr::null_mut(),
                          0);
         }
         if cpus < 1 {
             cpus = 1;
         }
     }
     cpus as usize
 }

 #[cfg(target_os = "openbsd")]
 fn get_num_cpus() -> usize {
     use std::ptr;

     let mut cpus: libc::c_uint = 0;
     let mut cpus_size = std::mem::size_of_val(&cpus);
     let mut mib = [libc::CTL_HW, libc::HW_NCPUONLINE, 0, 0];
     let rc: libc::c_int;

     unsafe {
         rc = libc::sysctl(mib.as_mut_ptr(),
                           2,
                           &mut cpus as *mut _ as *mut _,
                           &mut cpus_size as *mut _ as *mut _,
                           ptr::null_mut(),
                           0);
     }
     if rc < 0 {
         cpus = 1;
     }
     cpus as usize
 }

 #[cfg(target_os = "openbsd")]
 fn get_num_physical_cpus() -> usize {
     use std::ptr;

     let mut cpus: libc::c_uint = 0;
     let mut cpus_size = std::mem::size_of_val(&cpus);
     let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
     let rc: libc::c_int;

     unsafe {
         rc = libc::sysctl(mib.as_mut_ptr(),
                           2,
                           &mut cpus as *mut _ as *mut _,
                           &mut cpus_size as *mut _ as *mut _,
                           ptr::null_mut(),
                           0);
     }
     if rc < 0 {
         cpus = 1;
     }
     cpus as usize
 }


 #[cfg(target_os = "macos")]
 fn get_num_physical_cpus() -> usize {
     use std::ffi::CStr;
     use std::ptr;

     let mut cpus: i32 = 0;
     let mut cpus_size = std::mem::size_of_val(&cpus);

     let sysctl_name = CStr::from_bytes_with_nul(b"hw.physicalcpu\0")
         .expect("byte literal is missing NUL");

     unsafe {
         if 0 != libc::sysctlbyname(sysctl_name.as_ptr(),
                                    &mut cpus as *mut _ as *mut _,
                                    &mut cpus_size as *mut _ as *mut _,
                                    ptr::null_mut(),
                                    0) {
             return get_num_cpus();
         }
     }
     cpus as usize
 }

 #[cfg(target_os = "aix")]
 fn get_num_physical_cpus() -> usize {
     match get_smt_threads_aix() {
         Some(num) => get_num_cpus() / num,
         None => get_num_cpus(),
     }
 }

 #[cfg(target_os = "aix")]
 fn get_smt_threads_aix() -> Option<usize> {
     let smt = unsafe {
         libc::getsystemcfg(libc::SC_SMT_TC)
     };
     if smt == u64::MAX {
         return None;
     }
     Some(smt as usize)
 }

 #[cfg(any(
     target_os = "nacl",
     target_os = "macos",
     target_os = "ios",
     target_os = "android",
     target_os = "aix",
     target_os = "solaris",
     target_os = "illumos",
     target_os = "fuchsia")
 )]
 fn get_num_cpus() -> usize {
     // On ARM targets, processors could be turned off to save power.
     // Use `_SC_NPROCESSORS_CONF` to get the real number.
     #[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
     const CONF_NAME: libc::c_int = libc::_SC_NPROCESSORS_CONF;
     #[cfg(not(any(target_arch = "arm", target_arch = "aarch64")))]
     const CONF_NAME: libc::c_int = libc::_SC_NPROCESSORS_ONLN;

     let cpus = unsafe { libc::sysconf(CONF_NAME) };
     if cpus < 1 {
         1
     } else {
         cpus as usize
     }
 }

 #[cfg(target_os = "haiku")]
 fn get_num_cpus() -> usize {
     use std::mem;

     #[allow(non_camel_case_types)]
     type bigtime_t = i64;
     #[allow(non_camel_case_types)]
     type status_t = i32;

     #[repr(C)]
     pub struct system_info {
         pub boot_time: bigtime_t,
         pub cpu_count: u32,
         pub max_pages: u64,
         pub used_pages: u64,
         pub cached_pages: u64,
         pub block_cache_pages: u64,
         pub ignored_pages: u64,
         pub needed_memory: u64,
         pub free_memory: u64,
         pub max_swap_pages: u64,
         pub free_swap_pages: u64,
         pub page_faults: u32,
         pub max_sems: u32,
         pub used_sems: u32,
         pub max_ports: u32,
         pub used_ports: u32,
         pub max_threads: u32,
         pub used_threads: u32,
         pub max_teams: u32,
         pub used_teams: u32,
         pub kernel_name: [::std::os::raw::c_char; 256usize],
         pub kernel_build_date: [::std::os::raw::c_char; 32usize],
         pub kernel_build_time: [::std::os::raw::c_char; 32usize],
         pub kernel_version: i64,
         pub abi: u32,
     }

     extern {
         fn get_system_info(info: *mut system_info) -> status_t;
     }

     let mut info: system_info = unsafe { mem::zeroed() };
     let status = unsafe { get_system_info(&mut info as *mut _) };
     if status == 0 {
         info.cpu_count as usize
     } else {
         1
     }
 }

 #[cfg(target_os = "hermit")]
 fn get_num_cpus() -> usize {
     unsafe { hermit_abi::get_processor_count() }
 }

 #[cfg(not(any(
     target_os = "nacl",
     target_os = "macos",
     target_os = "ios",
     target_os = "android",
     target_os = "aix",
     target_os = "solaris",
     target_os = "illumos",
     target_os = "fuchsia",
     target_os = "linux",
     target_os = "openbsd",
     target_os = "freebsd",
     target_os = "dragonfly",
     target_os = "netbsd",
     target_os = "haiku",
     target_os = "hermit",
     windows,
 )))]
 fn get_num_cpus() -> usize {
     1
 }

 #[cfg(test)]
 mod tests {
     fn env_var(name: &'static str) -> Option<usize> {
         ::std::env::var(name).ok().map(|val| val.parse().unwrap())
     }

     #[test]
     fn test_get() {
         let num = super::get();
         if let Some(n) = env_var("NUM_CPUS_TEST_GET") {
             assert_eq!(num, n);
         } else {
             assert!(num > 0);
             assert!(num < 236_451);
         }
     }

     #[test]
     fn test_get_physical() {
         let num = super::get_physical();
         if let Some(n) = env_var("NUM_CPUS_TEST_GET_PHYSICAL") {
             assert_eq!(num, n);
         } else {
             assert!(num > 0);
             assert!(num < 236_451);
         }
     }
 }
	//! A crate with utilities to determine the number of CPUs available on the
	//! current system.
	//!
	//! Sometimes the CPU will exaggerate the number of CPUs it contains, because it can use
	//! [processor tricks] to deliver increased performance when there are more threads. This
	//! crate provides methods to get both the logical and physical numbers of cores.
	//!
	//! This information can be used as a guide to how many tasks can be run in parallel.
	//! There are many properties of the system architecture that will affect parallelism,
	//! for example memory access speeds (for all the caches and RAM) and the physical
	//! architecture of the processor, so the number of CPUs should be used as a rough guide
	//! only.
	//!
	//!
	//! ## Examples
	//!
	//! Fetch the number of logical CPUs.
	//!
	//! ```
	//! let cpus = num_cpus::get();
	//! ```
	//!
	//! See [`rayon::Threadpool`] for an example of where the number of CPUs could be
	//! used when setting up parallel jobs (Where the threadpool example uses a fixed
	//! number 8, it could use the number of CPUs).
	//!
	//! [processor tricks]: https://en.wikipedia.org/wiki/Simultaneous_multithreading
	//! [`rayon::ThreadPool`]: https://docs.rs/rayon/1.*/rayon/struct.ThreadPool.html
	#![cfg_attr(test, deny(warnings))]
	#![deny(missing_docs)]
	#![allow(non_snake_case)]

	#[cfg(not(windows))]
	extern crate libc;

	#[cfg(target_os = "hermit")]
	extern crate hermit_abi;

	#[cfg(target_os = "linux")]
	mod linux;
	#[cfg(target_os = "linux")]
	use linux::{get_num_cpus, get_num_physical_cpus};

	/// Returns the number of available CPUs of the current system.
	///
	/// This function will get the number of logical cores. Sometimes this is different from the number
	/// of physical cores (See [Simultaneous multithreading on Wikipedia][smt]).
	///
	/// This will always return at least `1`.
	///
	/// # Examples
	///
	/// ```
	/// let cpus = num_cpus::get();
	/// if cpus > 1 {
	/// println!("We are on a multicore system with {} CPUs", cpus);
	/// } else {
	/// println!("We are on a single core system");
	/// }
	/// ```
	///
	/// # Note
	///
	/// This will check [sched affinity] on Linux, showing a lower number of CPUs if the current
	/// thread does not have access to all the computer's CPUs.
	///
	/// This will also check [cgroups], frequently used in containers to constrain CPU usage.
	///
	/// [smt]: https://en.wikipedia.org/wiki/Simultaneous_multithreading
	/// [sched affinity]: http://www.gnu.org/software/libc/manual/html_node/CPU-Affinity.html
	/// [cgroups]: https://www.kernel.org/doc/Documentation/cgroup-v1/cgroups.txt
	#[inline]
	pub fn get() -> usize {
	get_num_cpus()
	}

	/// Returns the number of physical cores of the current system.
	///
	/// This will always return at least `1`.
	///
	/// # Note
	///
	/// Physical count is supported only on Linux, mac OS and Windows platforms.
	/// On other platforms, or if the physical count fails on supported platforms,
	/// this function returns the same as [`get()`], which is the number of logical
	/// CPUS.
	///
	/// # Examples
	///
	/// ```
	/// let logical_cpus = num_cpus::get();
	/// let physical_cpus = num_cpus::get_physical();
	/// if logical_cpus > physical_cpus {
	/// println!("We have simultaneous multithreading with about {:.2} \
	/// logical cores to 1 physical core.",
	/// (logical_cpus as f64) / (physical_cpus as f64));
	/// } else if logical_cpus == physical_cpus {
	/// println!("Either we don't have simultaneous multithreading, or our \
	/// system doesn't support getting the number of physical CPUs.");
	/// } else {
	/// println!("We have less logical CPUs than physical CPUs, maybe we only have access to \
	/// some of the CPUs on our system.");
	/// }
	/// ```
	///
	/// [`get()`]: fn.get.html
	#[inline]
	pub fn get_physical() -> usize {
	get_num_physical_cpus()
	}


	#[cfg(not(any(
	target_os = "linux",
	target_os = "windows",
	target_os = "macos",
	target_os = "openbsd",
	target_os = "aix")))]
	#[inline]
	fn get_num_physical_cpus() -> usize {
	// Not implemented, fall back
	get_num_cpus()
	}

	#[cfg(target_os = "windows")]
	fn get_num_physical_cpus() -> usize {
	match get_num_physical_cpus_windows() {
	Some(num) => num,
	None => get_num_cpus()
	}
	}

	#[cfg(target_os = "windows")]
	fn get_num_physical_cpus_windows() -> Option<usize> {
	// Inspired by https://msdn.microsoft.com/en-us/library/ms683194

	use std::ptr;
	use std::mem;

	#[allow(non_upper_case_globals)]
	const RelationProcessorCore: u32 = 0;

	#[repr(C)]
	#[allow(non_camel_case_types)]
	struct SYSTEM_LOGICAL_PROCESSOR_INFORMATION {
	mask: usize,
	relationship: u32,
	_unused: [u64; 2]
	}

	extern "system" {
	fn GetLogicalProcessorInformation(
	info: *mut SYSTEM_LOGICAL_PROCESSOR_INFORMATION,
	length: &mut u32
	) -> u32;
	}

	// First we need to determine how much space to reserve.

	// The required size of the buffer, in bytes.
	let mut needed_size = 0;

	unsafe {
	GetLogicalProcessorInformation(ptr::null_mut(), &mut needed_size);
	}

	let struct_size = mem::size_of::<SYSTEM_LOGICAL_PROCESSOR_INFORMATION>() as u32;

	// Could be 0, or some other bogus size.
	if needed_size == 0 \|\| needed_size < struct_size \|\| needed_size % struct_size != 0 {
	return None;
	}

	let count = needed_size / struct_size;

	// Allocate some memory where we will store the processor info.
	let mut buf = Vec::with_capacity(count as usize);

	let result;

	unsafe {
	result = GetLogicalProcessorInformation(buf.as_mut_ptr(), &mut needed_size);
	}

	// Failed for any reason.
	if result == 0 {
	return None;
	}

	let count = needed_size / struct_size;

	unsafe {
	buf.set_len(count as usize);
	}

	let phys_proc_count = buf.iter()
	// Only interested in processor packages (physical processors.)
	.filter(\|proc_info\| proc_info.relationship == RelationProcessorCore)
	.count();

	if phys_proc_count == 0 {
	None
	} else {
	Some(phys_proc_count)
	}
	}

	#[cfg(windows)]
	fn get_num_cpus() -> usize {
	#[repr(C)]
	struct SYSTEM_INFO {
	wProcessorArchitecture: u16,
	wReserved: u16,
	dwPageSize: u32,
	lpMinimumApplicationAddress: *mut u8,
	lpMaximumApplicationAddress: *mut u8,
	dwActiveProcessorMask: *mut u8,
	dwNumberOfProcessors: u32,
	dwProcessorType: u32,
	dwAllocationGranularity: u32,
	wProcessorLevel: u16,
	wProcessorRevision: u16,
	}

	extern "system" {
	fn GetSystemInfo(lpSystemInfo: *mut SYSTEM_INFO);
	}

	unsafe {
	let mut sysinfo: SYSTEM_INFO = std::mem::zeroed();
	GetSystemInfo(&mut sysinfo);
	sysinfo.dwNumberOfProcessors as usize
	}
	}

	#[cfg(any(target_os = "freebsd",
	target_os = "dragonfly",
	target_os = "netbsd"))]
	fn get_num_cpus() -> usize {
	use std::ptr;

	let mut cpus: libc::c_uint = 0;
	let mut cpus_size = std::mem::size_of_val(&cpus);

	unsafe {
	cpus = libc::sysconf(libc::_SC_NPROCESSORS_ONLN) as libc::c_uint;
	}
	if cpus < 1 {
	let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
	unsafe {
	libc::sysctl(mib.as_mut_ptr(),
	2,
	&mut cpus as mut _ as mut _,
	&mut cpus_size as mut _ as mut _,
	ptr::null_mut(),
	0);
	}
	if cpus < 1 {
	cpus = 1;
	}
	}
	cpus as usize
	}

	#[cfg(target_os = "openbsd")]
	fn get_num_cpus() -> usize {
	use std::ptr;

	let mut cpus: libc::c_uint = 0;
	let mut cpus_size = std::mem::size_of_val(&cpus);
	let mut mib = [libc::CTL_HW, libc::HW_NCPUONLINE, 0, 0];
	let rc: libc::c_int;

	unsafe {
	rc = libc::sysctl(mib.as_mut_ptr(),
	2,
	&mut cpus as mut _ as mut _,
	&mut cpus_size as mut _ as mut _,
	ptr::null_mut(),
	0);
	}
	if rc < 0 {
	cpus = 1;
	}
	cpus as usize
	}

	#[cfg(target_os = "openbsd")]
	fn get_num_physical_cpus() -> usize {
	use std::ptr;

	let mut cpus: libc::c_uint = 0;
	let mut cpus_size = std::mem::size_of_val(&cpus);
	let mut mib = [libc::CTL_HW, libc::HW_NCPU, 0, 0];
	let rc: libc::c_int;

	unsafe {
	rc = libc::sysctl(mib.as_mut_ptr(),
	2,
	&mut cpus as mut _ as mut _,
	&mut cpus_size as mut _ as mut _,
	ptr::null_mut(),
	0);
	}
	if rc < 0 {
	cpus = 1;
	}
	cpus as usize
	}


	#[cfg(target_os = "macos")]
	fn get_num_physical_cpus() -> usize {
	use std::ffi::CStr;
	use std::ptr;

	let mut cpus: i32 = 0;
	let mut cpus_size = std::mem::size_of_val(&cpus);

	let sysctl_name = CStr::from_bytes_with_nul(b"hw.physicalcpu\0")
	.expect("byte literal is missing NUL");

	unsafe {
	if 0 != libc::sysctlbyname(sysctl_name.as_ptr(),
	&mut cpus as mut _ as mut _,
	&mut cpus_size as mut _ as mut _,
	ptr::null_mut(),
	0) {
	return get_num_cpus();
	}
	}
	cpus as usize
	}

	#[cfg(target_os = "aix")]
	fn get_num_physical_cpus() -> usize {
	match get_smt_threads_aix() {
	Some(num) => get_num_cpus() / num,
	None => get_num_cpus(),
	}
	}

	#[cfg(target_os = "aix")]
	fn get_smt_threads_aix() -> Option<usize> {
	let smt = unsafe {
	libc::getsystemcfg(libc::SC_SMT_TC)
	};
	if smt == u64::MAX {
	return None;
	}
	Some(smt as usize)
	}

	#[cfg(any(
	target_os = "nacl",
	target_os = "macos",
	target_os = "ios",
	target_os = "android",
	target_os = "aix",
	target_os = "solaris",
	target_os = "illumos",
	target_os = "fuchsia")
	)]
	fn get_num_cpus() -> usize {
	// On ARM targets, processors could be turned off to save power.
	// Use `_SC_NPROCESSORS_CONF` to get the real number.
	#[cfg(any(target_arch = "arm", target_arch = "aarch64"))]
	const CONF_NAME: libc::c_int = libc::_SC_NPROCESSORS_CONF;
	#[cfg(not(any(target_arch = "arm", target_arch = "aarch64")))]
	const CONF_NAME: libc::c_int = libc::_SC_NPROCESSORS_ONLN;

	let cpus = unsafe { libc::sysconf(CONF_NAME) };
	if cpus < 1 {
	1
	} else {
	cpus as usize
	}
	}

	#[cfg(target_os = "haiku")]
	fn get_num_cpus() -> usize {
	use std::mem;

	#[allow(non_camel_case_types)]
	type bigtime_t = i64;
	#[allow(non_camel_case_types)]
	type status_t = i32;

	#[repr(C)]
	pub struct system_info {
	pub boot_time: bigtime_t,
	pub cpu_count: u32,
	pub max_pages: u64,
	pub used_pages: u64,
	pub cached_pages: u64,
	pub block_cache_pages: u64,
	pub ignored_pages: u64,
	pub needed_memory: u64,
	pub free_memory: u64,
	pub max_swap_pages: u64,
	pub free_swap_pages: u64,
	pub page_faults: u32,
	pub max_sems: u32,
	pub used_sems: u32,
	pub max_ports: u32,
	pub used_ports: u32,
	pub max_threads: u32,
	pub used_threads: u32,
	pub max_teams: u32,
	pub used_teams: u32,
	pub kernel_name: [::std::os::raw::c_char; 256usize],
	pub kernel_build_date: [::std::os::raw::c_char; 32usize],
	pub kernel_build_time: [::std::os::raw::c_char; 32usize],
	pub kernel_version: i64,
	pub abi: u32,
	}

	extern {
	fn get_system_info(info: *mut system_info) -> status_t;
	}

	let mut info: system_info = unsafe { mem::zeroed() };
	let status = unsafe { get_system_info(&mut info as *mut _) };
	if status == 0 {
	info.cpu_count as usize
	} else {
	1
	}
	}

	#[cfg(target_os = "hermit")]
	fn get_num_cpus() -> usize {
	unsafe { hermit_abi::get_processor_count() }
	}

	#[cfg(not(any(
	target_os = "nacl",
	target_os = "macos",
	target_os = "ios",
	target_os = "android",
	target_os = "aix",
	target_os = "solaris",
	target_os = "illumos",
	target_os = "fuchsia",
	target_os = "linux",
	target_os = "openbsd",
	target_os = "freebsd",
	target_os = "dragonfly",
	target_os = "netbsd",
	target_os = "haiku",
	target_os = "hermit",
	windows,
	)))]
	fn get_num_cpus() -> usize {
	1
	}

	#[cfg(test)]
	mod tests {
	fn env_var(name: &'static str) -> Option<usize> {
	::std::env::var(name).ok().map(\|val\| val.parse().unwrap())
	}

	#[test]
	fn test_get() {
	let num = super::get();
	if let Some(n) = env_var("NUM_CPUS_TEST_GET") {
	assert_eq!(num, n);
	} else {
	assert!(num > 0);
	assert!(num < 236_451);
	}
	}

	#[test]
	fn test_get_physical() {
	let num = super::get_physical();
	if let Some(n) = env_var("NUM_CPUS_TEST_GET_PHYSICAL") {
	assert_eq!(num, n);
	} else {
	assert!(num > 0);
	assert!(num < 236_451);
	}
	}
	}