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//! Environmental management
//!
//! This module provides ways for an MPI program to interact with its environment.
//!
//! # Unfinished features
//!
//! - **8.1.2**: `MPI_TAG_UB`, ...
//! - **8.2**: Memory allocation
//! - **8.3, 8.4, and 8.5**: Error handling
use std::{
cmp::Ordering,
os::raw::{c_char, c_double, c_int, c_void},
ptr,
string::FromUtf8Error,
sync::RwLock,
thread::{self, ThreadId},
};
use conv::ConvUtil;
use once_cell::sync::Lazy;
use crate::traits::FromRaw;
use crate::{ffi, topology::SystemAttribute};
use crate::{
topology::{Communicator, InterCommunicator, SimpleCommunicator},
traits::AsRaw,
};
use crate::{with_uninitialized, with_uninitialized2};
/// Internal data structure used to uphold certain MPI invariants.
/// State is currently only used with the derive feature.
pub(crate) struct UniverseState {
#[allow(unused)]
pub main_thread: ThreadId,
}
pub(crate) static UNIVERSE_STATE: Lazy<RwLock<Option<UniverseState>>> =
Lazy::new(|| RwLock::new(None));
/// Global context
pub struct Universe {
buffer: Option<Vec<u8>>,
}
impl Universe {
/// The 'world communicator'
///
/// Contains all processes initially partaking in the computation.
///
/// # Examples
/// See `examples/simple.rs`
pub fn world(&self) -> SimpleCommunicator {
SimpleCommunicator::world()
}
/// Total number of "slots" that can reasonably be filled in the environment
///
/// This can be larger or smaller than the world (e.g., when
/// oversubscribed). The universe size is generally not a hard limit. A
/// universe size need not be set. To specify universe size, MPICH mpiexec
/// supports the command line option `-usize 123` and Open MPI supports the
/// environment variable `OMPI_UNIVERSE_SIZE=123`.
///
/// # Standard section(s)
///
/// 11.10.1
pub fn size(&self) -> Option<usize> {
// self.world().get_attr()
let attr = unsafe { SystemAttribute::from_raw_unchecked(ffi::MPI_UNIVERSE_SIZE as i32) };
self.world()
.get_attr(attr)
.map(|s| usize::try_from(*s).expect("universe size must be non-negative"))
}
/// The size in bytes of the buffer used for buffered communication.
pub fn buffer_size(&self) -> usize {
self.buffer.as_ref().map_or(0, Vec::len)
}
/// Set the size in bytes of the buffer used for buffered communication.
pub fn set_buffer_size(&mut self, size: usize) {
self.detach_buffer();
if size > 0 {
let mut buffer = vec![0; size];
unsafe {
ffi::MPI_Buffer_attach(
buffer.as_mut_ptr() as _,
buffer
.len()
.value_as()
.expect("Buffer length exceeds the range of a C int."),
);
}
self.buffer = Some(buffer);
}
}
/// Detach the buffer used for buffered communication.
pub fn detach_buffer(&mut self) {
if let Some(buffer) = self.buffer.take() {
let mut addr: *const c_void = ptr::null();
let addr_ptr: *mut *const c_void = &mut addr;
let mut size: c_int = 0;
unsafe {
ffi::MPI_Buffer_detach(addr_ptr as *mut c_void, &mut size);
assert_eq!(addr, buffer.as_ptr() as _);
}
assert_eq!(
size,
buffer
.len()
.value_as()
.expect("Buffer length exceeds the range of a C int.")
);
}
}
/// Disconnect parent
///
/// MPICH can be configured to print leaked MPI objects. At this time (circa
/// 4.1b1), it reports a leak if a child process exits without freeing the
/// parent. This seems overly aggressive given the following.
///
/// Advice to users.
/// MPI_COMM_GET_PARENT returns a handle to a single inter-
/// communicator. Calling MPI_COMM_GET_PARENT a second time returns a handle
/// to the same inter-communicator. Freeing the handle with MPI_COMM_DISCONNECT
/// or MPI_COMM_FREE will cause other references to the inter-communicator to become
/// invalid (dangling). Note that calling MPI_COMM_FREE on the parent communicator
/// is not useful.
///
/// # Standard section(s)
///
/// 11.8.2
pub fn disconnect_parent(&mut self) {
if let Some(parent) = self.world().parent() {
// Make it look like a user communicator so it can be dropped
let _p = unsafe { InterCommunicator::from_raw(parent.as_raw()) };
}
}
}
impl Drop for Universe {
fn drop(&mut self) {
// This can only ever be called once since it's only possible to initialize a single
// Universe per application run.
//
// NOTE: The write lock is taken to prevent racing with `#[derive(Equivalence)]`
let mut _universe_state = UNIVERSE_STATE
.write()
.expect("rsmpi internal error: UNIVERSE_STATE lock poisoned");
self.detach_buffer();
self.disconnect_parent();
unsafe {
ffi::MPI_Finalize();
}
}
}
/// Describes the various levels of multithreading that can be supported by an MPI library.
///
/// # Examples
/// See `examples/init_with_threading.rs`
///
/// # Standard section(s)
///
/// 12.4.3
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
pub enum Threading {
/// All processes partaking in the computation are single-threaded.
Single,
/// Processes may be multi-threaded, but MPI functions will only ever be called from the main
/// thread.
Funneled,
/// Processes may be multi-threaded, but calls to MPI functions will not be made concurrently.
/// The user is responsible for serializing the calls.
Serialized,
/// Processes may be multi-threaded with no restrictions on the use of MPI functions from the
/// threads.
Multiple,
}
impl Threading {
/// The raw value understood by the MPI C API
fn as_raw(self) -> c_int {
match self {
Threading::Single => unsafe { ffi::RSMPI_THREAD_SINGLE },
Threading::Funneled => unsafe { ffi::RSMPI_THREAD_FUNNELED },
Threading::Serialized => unsafe { ffi::RSMPI_THREAD_SERIALIZED },
Threading::Multiple => unsafe { ffi::RSMPI_THREAD_MULTIPLE },
}
}
}
impl PartialOrd<Threading> for Threading {
fn partial_cmp(&self, other: &Threading) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl Ord for Threading {
fn cmp(&self, other: &Threading) -> Ordering {
self.as_raw().cmp(&other.as_raw())
}
}
impl From<c_int> for Threading {
fn from(i: c_int) -> Threading {
if i == unsafe { ffi::RSMPI_THREAD_SINGLE } {
return Threading::Single;
} else if i == unsafe { ffi::RSMPI_THREAD_FUNNELED } {
return Threading::Funneled;
} else if i == unsafe { ffi::RSMPI_THREAD_SERIALIZED } {
return Threading::Serialized;
} else if i == unsafe { ffi::RSMPI_THREAD_MULTIPLE } {
return Threading::Multiple;
}
panic!("Unknown threading level: {}", i)
}
}
/// Whether the MPI library has been initialized
pub(crate) fn is_initialized() -> bool {
unsafe { with_uninitialized(|initialized| ffi::MPI_Initialized(initialized)).1 != 0 }
}
/// Whether the MPI library has been initialized
/// NOTE: Used by "derive" feature
#[allow(unused)]
pub(crate) fn is_finalized() -> bool {
unsafe { with_uninitialized(|finalized| ffi::MPI_Finalized(finalized)).1 != 0 }
}
/// Initialize MPI.
///
/// If the MPI library has not been initialized so far, initializes and returns a representation
/// of the MPI communication `Universe` which provides access to additional functions.
/// Otherwise returns `None`.
///
/// Equivalent to: `initialize_with_threading(Threading::Single)`
///
/// # Examples
/// See `examples/simple.rs`
///
/// # Standard section(s)
///
/// 8.7
pub fn initialize() -> Option<Universe> {
initialize_with_threading(Threading::Single).map(|x| x.0)
}
/// Initialize MPI with desired level of multithreading support.
///
/// If the MPI library has not been initialized so far, tries to initialize with the desired level
/// of multithreading support and returns the MPI communication `Universe` with access to
/// additional functions as well as the level of multithreading actually supported by the
/// implementation. Otherwise returns `None`.
///
/// # Examples
/// See `examples/init_with_threading.rs`
///
/// # Standard section(s)
///
/// 12.4.3
pub fn initialize_with_threading(threading: Threading) -> Option<(Universe, Threading)> {
// Takes the lock before checking if MPI is initialized to prevent a race condition
// leading to two threads both calling `MPI_Init_thread` at the same time.
//
// NOTE: This is necessary even without the derive feature - we use this `Mutex` to ensure
// no race in initializing MPI.
let mut universe_state = UNIVERSE_STATE
.write()
.expect("rsmpi internal error: UNIVERSE_STATE lock poisoned");
if is_initialized() {
return None;
}
let (_, provided) = unsafe {
with_uninitialized(|provided| {
ffi::MPI_Init_thread(
ptr::null_mut(),
ptr::null_mut(),
threading.as_raw(),
provided,
)
})
};
// No need to check if UNIVERSE_STATE has already been set - only one thread can enter this
// code section per MPI run thanks to the `is_initialized()` check before.
*universe_state = Some(UniverseState {
main_thread: thread::current().id(),
});
Some((Universe { buffer: None }, provided.into()))
}
/// Level of multithreading supported by this MPI universe
///
/// See the `Threading` enum.
///
/// # Examples
/// See `examples/init_with_threading.rs`
pub fn threading_support() -> Threading {
unsafe {
with_uninitialized(|threading| ffi::MPI_Query_thread(threading))
.1
.into()
}
}
/// Identifies the version of the MPI standard implemented by the library.
///
/// Returns a tuple of `(version, subversion)`, e.g. `(3, 0)`.
///
/// Can be called without initializing MPI.
pub fn version() -> (c_int, c_int) {
let (_, version, subversion) = unsafe {
with_uninitialized2(|version, subversion| ffi::MPI_Get_version(version, subversion))
};
(version, subversion)
}
/// Describes the version of the MPI library itself.
///
/// Can return an `Err` if the description of the MPI library is not a UTF-8 string.
///
/// Can be called without initializing MPI.
pub fn library_version() -> Result<String, FromUtf8Error> {
let bufsize = unsafe { ffi::RSMPI_MAX_LIBRARY_VERSION_STRING }
.value_as()
.unwrap_or_else(|_| {
panic!(
"MPI_MAX_LIBRARY_SIZE ({}) cannot be expressed as a usize.",
unsafe { ffi::RSMPI_MAX_LIBRARY_VERSION_STRING }
)
});
let mut buf = vec![0u8; bufsize];
let mut len: c_int = 0;
unsafe {
ffi::MPI_Get_library_version(buf.as_mut_ptr() as *mut c_char, &mut len);
}
buf.truncate(len.value_as().unwrap_or_else(|_| {
panic!(
"Length of library version string ({}) cannot \
be expressed as a usize.",
len
)
}));
String::from_utf8(buf)
}
/// Names the processor that the calling process is running on.
///
/// Can return an `Err` if the processor name is not a UTF-8 string.
pub fn processor_name() -> Result<String, FromUtf8Error> {
let bufsize = unsafe { ffi::RSMPI_MAX_PROCESSOR_NAME }
.value_as()
.unwrap_or_else(|_| {
panic!(
"MPI_MAX_LIBRARY_SIZE ({}) \
cannot be expressed as a \
usize.",
unsafe { ffi::RSMPI_MAX_PROCESSOR_NAME }
)
});
let mut buf = vec![0u8; bufsize];
let mut len: c_int = 0;
unsafe {
ffi::MPI_Get_processor_name(buf.as_mut_ptr() as *mut c_char, &mut len);
}
buf.truncate(len.value_as().unwrap_or_else(|_| {
panic!(
"Length of processor name string ({}) cannot be \
expressed as a usize.",
len
)
}));
String::from_utf8(buf)
}
/// Time in seconds since an arbitrary time in the past.
///
/// The cheapest high-resolution timer available will be used.
pub fn time() -> c_double {
unsafe { ffi::RSMPI_Wtime() }
}
/// Resolution of timer used in `time()` in seconds
pub fn time_resolution() -> c_double {
unsafe { ffi::RSMPI_Wtick() }
}