"""threadpoolctl This module provides utilities to introspect native libraries that relies on thread pools (notably BLAS and OpenMP implementations) and dynamically set the maximal number of threads they can use. """ # License: BSD 3-Clause # The code to introspect dynamically loaded libraries on POSIX systems is # adapted from code by Intel developer @anton-malakhov available at # https://github.com/IntelPython/smp (Copyright (c) 2017, Intel Corporation) # and also published under the BSD 3-Clause license import os import re import sys import ctypes import itertools import textwrap from typing import final import warnings from ctypes.util import find_library from abc import ABC, abstractmethod from functools import lru_cache from contextlib import ContextDecorator __version__ = "3.5.0" __all__ = [ "threadpool_limits", "threadpool_info", "ThreadpoolController", "LibController", "register", ] # One can get runtime errors or even segfaults due to multiple OpenMP libraries # loaded simultaneously which can happen easily in Python when importing and # using compiled extensions built with different compilers and therefore # different OpenMP runtimes in the same program. In particular libiomp (used by # Intel ICC) and libomp used by clang/llvm tend to crash. This can happen for # instance when calling BLAS inside a prange. Setting the following environment # variable allows multiple OpenMP libraries to be loaded. It should not degrade # performances since we manually take care of potential over-subscription # performance issues, in sections of the code where nested OpenMP loops can # happen, by dynamically reconfiguring the inner OpenMP runtime to temporarily # disable it while under the scope of the outer OpenMP parallel section. os.environ.setdefault("KMP_DUPLICATE_LIB_OK", "True") # Structure to cast the info on dynamically loaded library. See # https://linux.die.net/man/3/dl_iterate_phdr for more details. _SYSTEM_UINT = ctypes.c_uint64 if sys.maxsize > 2**32 else ctypes.c_uint32 _SYSTEM_UINT_HALF = ctypes.c_uint32 if sys.maxsize > 2**32 else ctypes.c_uint16 class _dl_phdr_info(ctypes.Structure): _fields_ = [ ("dlpi_addr", _SYSTEM_UINT), # Base address of object ("dlpi_name", ctypes.c_char_p), # path to the library ("dlpi_phdr", ctypes.c_void_p), # pointer on dlpi_headers ("dlpi_phnum", _SYSTEM_UINT_HALF), # number of elements in dlpi_phdr ] # The RTLD_NOLOAD flag for loading shared libraries is not defined on Windows. try: _RTLD_NOLOAD = os.RTLD_NOLOAD except AttributeError: _RTLD_NOLOAD = ctypes.DEFAULT_MODE class LibController(ABC): """Abstract base class for the individual library controllers A library controller must expose the following class attributes: - user_api : str Usually the name of the library or generic specification the library implements, e.g. "blas" is a specification with different implementations. - internal_api : str Usually the name of the library or concrete implementation of some specification, e.g. "openblas" is an implementation of the "blas" specification. - filename_prefixes : tuple Possible prefixes of the shared library's filename that allow to identify the library. e.g. "libopenblas" for libopenblas.so. and implement the following methods: `get_num_threads`, `set_num_threads` and `get_version`. Threadpoolctl loops through all the loaded shared libraries and tries to match the filename of each library with the `filename_prefixes`. If a match is found, a controller is instantiated and a handler to the library is stored in the `dynlib` attribute as a `ctypes.CDLL` object. It can be used to access the necessary symbols of the shared library to implement the above methods. The following information will be exposed in the info dictionary: - user_api : standardized API, if any, or a copy of internal_api. - internal_api : implementation-specific API. - num_threads : the current thread limit. - prefix : prefix of the shared library's filename. - filepath : path to the loaded shared library. - version : version of the library (if available). In addition, each library controller may expose internal API specific entries. They must be set as attributes in the `set_additional_attributes` method. """ @final def __init__(self, *, filepath=None, prefix=None, parent=None): """This is not meant to be overriden by subclasses.""" self.parent = parent self.prefix = prefix self.filepath = filepath self.dynlib = ctypes.CDLL(filepath, mode=_RTLD_NOLOAD) self._symbol_prefix, self._symbol_suffix = self._find_affixes() self.version = self.get_version() self.set_additional_attributes() def info(self): """Return relevant info wrapped in a dict""" hidden_attrs = ("dynlib", "parent", "_symbol_prefix", "_symbol_suffix") return { "user_api": self.user_api, "internal_api": self.internal_api, "num_threads": self.num_threads, **{k: v for k, v in vars(self).items() if k not in hidden_attrs}, } def set_additional_attributes(self): """Set additional attributes meant to be exposed in the info dict""" @property def num_threads(self): """Exposes the current thread limit as a dynamic property This is not meant to be used or overriden by subclasses. """ return self.get_num_threads() @abstractmethod def get_num_threads(self): """Return the maximum number of threads available to use""" @abstractmethod def set_num_threads(self, num_threads): """Set the maximum number of threads to use""" @abstractmethod def get_version(self): """Return the version of the shared library""" def _find_affixes(self): """Return the affixes for the symbols of the shared library""" return "", "" def _get_symbol(self, name): """Return the symbol of the shared library accounding for the affixes""" return getattr( self.dynlib, f"{self._symbol_prefix}{name}{self._symbol_suffix}", None ) class OpenBLASController(LibController): """Controller class for OpenBLAS""" user_api = "blas" internal_api = "openblas" filename_prefixes = ("libopenblas", "libblas", "libscipy_openblas") _symbol_prefixes = ("", "scipy_") _symbol_suffixes = ("", "64_", "_64") # All variations of "openblas_get_num_threads", accounting for the affixes check_symbols = tuple( f"{prefix}openblas_get_num_threads{suffix}" for prefix, suffix in itertools.product(_symbol_prefixes, _symbol_suffixes) ) def _find_affixes(self): for prefix, suffix in itertools.product( self._symbol_prefixes, self._symbol_suffixes ): if hasattr(self.dynlib, f"{prefix}openblas_get_num_threads{suffix}"): return prefix, suffix def set_additional_attributes(self): self.threading_layer = self._get_threading_layer() self.architecture = self._get_architecture() def get_num_threads(self): get_num_threads_func = self._get_symbol("openblas_get_num_threads") if get_num_threads_func is not None: return get_num_threads_func() return None def set_num_threads(self, num_threads): set_num_threads_func = self._get_symbol("openblas_set_num_threads") if set_num_threads_func is not None: return set_num_threads_func(num_threads) return None def get_version(self): # None means OpenBLAS is not loaded or version < 0.3.4, since OpenBLAS # did not expose its version before that. get_version_func = self._get_symbol("openblas_get_config") if get_version_func is not None: get_version_func.restype = ctypes.c_char_p config = get_version_func().split() if config[0] == b"OpenBLAS": return config[1].decode("utf-8") return None return None def _get_threading_layer(self): """Return the threading layer of OpenBLAS""" get_threading_layer_func = self._get_symbol("openblas_get_parallel") if get_threading_layer_func is not None: threading_layer = get_threading_layer_func() if threading_layer == 2: return "openmp" elif threading_layer == 1: return "pthreads" return "disabled" return "unknown" def _get_architecture(self): """Return the architecture detected by OpenBLAS""" get_architecture_func = self._get_symbol("openblas_get_corename") if get_architecture_func is not None: get_architecture_func.restype = ctypes.c_char_p return get_architecture_func().decode("utf-8") return None class BLISController(LibController): """Controller class for BLIS""" user_api = "blas" internal_api = "blis" filename_prefixes = ("libblis", "libblas") check_symbols = ( "bli_thread_get_num_threads", "bli_thread_set_num_threads", "bli_info_get_version_str", "bli_info_get_enable_openmp", "bli_info_get_enable_pthreads", "bli_arch_query_id", "bli_arch_string", ) def set_additional_attributes(self): self.threading_layer = self._get_threading_layer() self.architecture = self._get_architecture() def get_num_threads(self): get_func = getattr(self.dynlib, "bli_thread_get_num_threads", lambda: None) num_threads = get_func() # by default BLIS is single-threaded and get_num_threads # returns -1. We map it to 1 for consistency with other libraries. return 1 if num_threads == -1 else num_threads def set_num_threads(self, num_threads): set_func = getattr( self.dynlib, "bli_thread_set_num_threads", lambda num_threads: None ) return set_func(num_threads) def get_version(self): get_version_ = getattr(self.dynlib, "bli_info_get_version_str", None) if get_version_ is None: return None get_version_.restype = ctypes.c_char_p return get_version_().decode("utf-8") def _get_threading_layer(self): """Return the threading layer of BLIS""" if getattr(self.dynlib, "bli_info_get_enable_openmp", lambda: False)(): return "openmp" elif getattr(self.dynlib, "bli_info_get_enable_pthreads", lambda: False)(): return "pthreads" return "disabled" def _get_architecture(self): """Return the architecture detected by BLIS""" bli_arch_query_id = getattr(self.dynlib, "bli_arch_query_id", None) bli_arch_string = getattr(self.dynlib, "bli_arch_string", None) if bli_arch_query_id is None or bli_arch_string is None: return None # the true restype should be BLIS' arch_t (enum) but int should work # for us: bli_arch_query_id.restype = ctypes.c_int bli_arch_string.restype = ctypes.c_char_p return bli_arch_string(bli_arch_query_id()).decode("utf-8") class FlexiBLASController(LibController): """Controller class for FlexiBLAS""" user_api = "blas" internal_api = "flexiblas" filename_prefixes = ("libflexiblas",) check_symbols = ( "flexiblas_get_num_threads", "flexiblas_set_num_threads", "flexiblas_get_version", "flexiblas_list", "flexiblas_list_loaded", "flexiblas_current_backend", ) @property def loaded_backends(self): return self._get_backend_list(loaded=True) @property def current_backend(self): return self._get_current_backend() def info(self): """Return relevant info wrapped in a dict""" # We override the info method because the loaded and current backends # are dynamic properties exposed_attrs = super().info() exposed_attrs["loaded_backends"] = self.loaded_backends exposed_attrs["current_backend"] = self.current_backend return exposed_attrs def set_additional_attributes(self): self.available_backends = self._get_backend_list(loaded=False) def get_num_threads(self): get_func = getattr(self.dynlib, "flexiblas_get_num_threads", lambda: None) num_threads = get_func() # by default BLIS is single-threaded and get_num_threads # returns -1. We map it to 1 for consistency with other libraries. return 1 if num_threads == -1 else num_threads def set_num_threads(self, num_threads): set_func = getattr( self.dynlib, "flexiblas_set_num_threads", lambda num_threads: None ) return set_func(num_threads) def get_version(self): get_version_ = getattr(self.dynlib, "flexiblas_get_version", None) if get_version_ is None: return None major = ctypes.c_int() minor = ctypes.c_int() patch = ctypes.c_int() get_version_(ctypes.byref(major), ctypes.byref(minor), ctypes.byref(patch)) return f"{major.value}.{minor.value}.{patch.value}" def _get_backend_list(self, loaded=False): """Return the list of available backends for FlexiBLAS. If loaded is False, return the list of available backends from the FlexiBLAS configuration. If loaded is True, return the list of actually loaded backends. """ func_name = f"flexiblas_list{'_loaded' if loaded else ''}" get_backend_list_ = getattr(self.dynlib, func_name, None) if get_backend_list_ is None: return None n_backends = get_backend_list_(None, 0, 0) backends = [] for i in range(n_backends): backend_name = ctypes.create_string_buffer(1024) get_backend_list_(backend_name, 1024, i) if backend_name.value.decode("utf-8") != "__FALLBACK__": # We don't know when to expect __FALLBACK__ but it is not a real # backend and does not show up when running flexiblas list. backends.append(backend_name.value.decode("utf-8")) return backends def _get_current_backend(self): """Return the backend of FlexiBLAS""" get_backend_ = getattr(self.dynlib, "flexiblas_current_backend", None) if get_backend_ is None: return None backend = ctypes.create_string_buffer(1024) get_backend_(backend, ctypes.sizeof(backend)) return backend.value.decode("utf-8") def switch_backend(self, backend): """Switch the backend of FlexiBLAS Parameters ---------- backend : str The name or the path to the shared library of the backend to switch to. If the backend is not already loaded, it will be loaded first. """ if backend not in self.loaded_backends: if backend in self.available_backends: load_func = getattr(self.dynlib, "flexiblas_load_backend", lambda _: -1) else: # assume backend is a path to a shared library load_func = getattr( self.dynlib, "flexiblas_load_backend_library", lambda _: -1 ) res = load_func(str(backend).encode("utf-8")) if res == -1: raise RuntimeError( f"Failed to load backend {backend!r}. It must either be the name of" " a backend available in the FlexiBLAS configuration " f"{self.available_backends} or the path to a valid shared library." ) # Trigger a new search of loaded shared libraries since loading a new # backend caused a dlopen. self.parent._load_libraries() switch_func = getattr(self.dynlib, "flexiblas_switch", lambda _: -1) idx = self.loaded_backends.index(backend) res = switch_func(idx) if res == -1: raise RuntimeError(f"Failed to switch to backend {backend!r}.") class MKLController(LibController): """Controller class for MKL""" user_api = "blas" internal_api = "mkl" filename_prefixes = ("libmkl_rt", "mkl_rt", "libblas") check_symbols = ( "MKL_Get_Max_Threads", "MKL_Set_Num_Threads", "MKL_Get_Version_String", "MKL_Set_Threading_Layer", ) def set_additional_attributes(self): self.threading_layer = self._get_threading_layer() def get_num_threads(self): get_func = getattr(self.dynlib, "MKL_Get_Max_Threads", lambda: None) return get_func() def set_num_threads(self, num_threads): set_func = getattr(self.dynlib, "MKL_Set_Num_Threads", lambda num_threads: None) return set_func(num_threads) def get_version(self): if not hasattr(self.dynlib, "MKL_Get_Version_String"): return None res = ctypes.create_string_buffer(200) self.dynlib.MKL_Get_Version_String(res, 200) version = res.value.decode("utf-8") group = re.search(r"Version ([^ ]+) ", version) if group is not None: version = group.groups()[0] return version.strip() def _get_threading_layer(self): """Return the threading layer of MKL""" # The function mkl_set_threading_layer returns the current threading # layer. Calling it with an invalid threading layer allows us to safely # get the threading layer set_threading_layer = getattr( self.dynlib, "MKL_Set_Threading_Layer", lambda layer: -1 ) layer_map = { 0: "intel", 1: "sequential", 2: "pgi", 3: "gnu", 4: "tbb", -1: "not specified", } return layer_map[set_threading_layer(-1)] class OpenMPController(LibController): """Controller class for OpenMP""" user_api = "openmp" internal_api = "openmp" filename_prefixes = ("libiomp", "libgomp", "libomp", "vcomp") check_symbols = ( "omp_get_max_threads", "omp_get_num_threads", ) def get_num_threads(self): get_func = getattr(self.dynlib, "omp_get_max_threads", lambda: None) return get_func() def set_num_threads(self, num_threads): set_func = getattr(self.dynlib, "omp_set_num_threads", lambda num_threads: None) return set_func(num_threads) def get_version(self): # There is no way to get the version number programmatically in OpenMP. return None # Controllers for the libraries that we'll look for in the loaded libraries. # Third party libraries can register their own controllers. _ALL_CONTROLLERS = [ OpenBLASController, BLISController, MKLController, OpenMPController, FlexiBLASController, ] # Helpers for the doc and test names _ALL_USER_APIS = list(set(lib.user_api for lib in _ALL_CONTROLLERS)) _ALL_INTERNAL_APIS = [lib.internal_api for lib in _ALL_CONTROLLERS] _ALL_PREFIXES = list( set(prefix for lib in _ALL_CONTROLLERS for prefix in lib.filename_prefixes) ) _ALL_BLAS_LIBRARIES = [ lib.internal_api for lib in _ALL_CONTROLLERS if lib.user_api == "blas" ] _ALL_OPENMP_LIBRARIES = OpenMPController.filename_prefixes def register(controller): """Register a new controller""" _ALL_CONTROLLERS.append(controller) _ALL_USER_APIS.append(controller.user_api) _ALL_INTERNAL_APIS.append(controller.internal_api) _ALL_PREFIXES.extend(controller.filename_prefixes) def _format_docstring(*args, **kwargs): def decorator(o): if o.__doc__ is not None: o.__doc__ = o.__doc__.format(*args, **kwargs) return o return decorator @lru_cache(maxsize=10000) def _realpath(filepath): """Small caching wrapper around os.path.realpath to limit system calls""" return os.path.realpath(filepath) @_format_docstring(USER_APIS=list(_ALL_USER_APIS), INTERNAL_APIS=_ALL_INTERNAL_APIS) def threadpool_info(): """Return the maximal number of threads for each detected library. Return a list with all the supported libraries that have been found. Each library is represented by a dict with the following information: - "user_api" : user API. Possible values are {USER_APIS}. - "internal_api": internal API. Possible values are {INTERNAL_APIS}. - "prefix" : filename prefix of the specific implementation. - "filepath": path to the loaded library. - "version": version of the library (if available). - "num_threads": the current thread limit. In addition, each library may contain internal_api specific entries. """ return ThreadpoolController().info() class _ThreadpoolLimiter: """The guts of ThreadpoolController.limit Refer to the docstring of ThreadpoolController.limit for more details. It will only act on the library controllers held by the provided `controller`. Using the default constructor sets the limits right away such that it can be used as a callable. Setting the limits can be delayed by using the `wrap` class method such that it can be used as a decorator. """ def __init__(self, controller, *, limits=None, user_api=None): self._controller = controller self._limits, self._user_api, self._prefixes = self._check_params( limits, user_api ) self._original_info = self._controller.info() self._set_threadpool_limits() def __enter__(self): return self def __exit__(self, type, value, traceback): self.restore_original_limits() @classmethod def wrap(cls, controller, *, limits=None, user_api=None): """Return an instance of this class that can be used as a decorator""" return _ThreadpoolLimiterDecorator( controller=controller, limits=limits, user_api=user_api ) def restore_original_limits(self): """Set the limits back to their original values""" for lib_controller, original_info in zip( self._controller.lib_controllers, self._original_info ): lib_controller.set_num_threads(original_info["num_threads"]) # Alias of `restore_original_limits` for backward compatibility unregister = restore_original_limits def get_original_num_threads(self): """Original num_threads from before calling threadpool_limits Return a dict `{user_api: num_threads}`. """ num_threads = {} warning_apis = [] for user_api in self._user_api: limits = [ lib_info["num_threads"] for lib_info in self._original_info if lib_info["user_api"] == user_api ] limits = set(limits) n_limits = len(limits) if n_limits == 1: limit = limits.pop() elif n_limits == 0: limit = None else: limit = min(limits) warning_apis.append(user_api) num_threads[user_api] = limit if warning_apis: warnings.warn( "Multiple value possible for following user apis: " + ", ".join(warning_apis) + ". Returning the minimum." ) return num_threads def _check_params(self, limits, user_api): """Suitable values for the _limits, _user_api and _prefixes attributes""" if isinstance(limits, str) and limits == "sequential_blas_under_openmp": ( limits, user_api, ) = self._controller._get_params_for_sequential_blas_under_openmp().values() if limits is None or isinstance(limits, int): if user_api is None: user_api = _ALL_USER_APIS elif user_api in _ALL_USER_APIS: user_api = [user_api] else: raise ValueError( f"user_api must be either in {_ALL_USER_APIS} or None. Got " f"{user_api} instead." ) if limits is not None: limits = {api: limits for api in user_api} prefixes = [] else: if isinstance(limits, list): # This should be a list of dicts of library info, for # compatibility with the result from threadpool_info. limits = { lib_info["prefix"]: lib_info["num_threads"] for lib_info in limits } elif isinstance(limits, ThreadpoolController): # To set the limits from the library controllers of a # ThreadpoolController object. limits = { lib_controller.prefix: lib_controller.num_threads for lib_controller in limits.lib_controllers } if not isinstance(limits, dict): raise TypeError( "limits must either be an int, a list, a dict, or " f"'sequential_blas_under_openmp'. Got {type(limits)} instead" ) # With a dictionary, can set both specific limit for given # libraries and global limit for user_api. Fetch each separately. prefixes = [prefix for prefix in limits if prefix in _ALL_PREFIXES] user_api = [api for api in limits if api in _ALL_USER_APIS] return limits, user_api, prefixes def _set_threadpool_limits(self): """Change the maximal number of threads in selected thread pools. Return a list with all the supported libraries that have been found matching `self._prefixes` and `self._user_api`. """ if self._limits is None: return for lib_controller in self._controller.lib_controllers: # self._limits is a dict {key: num_threads} where key is either # a prefix or a user_api. If a library matches both, the limit # corresponding to the prefix is chosen. if lib_controller.prefix in self._limits: num_threads = self._limits[lib_controller.prefix] elif lib_controller.user_api in self._limits: num_threads = self._limits[lib_controller.user_api] else: continue if num_threads is not None: lib_controller.set_num_threads(num_threads) class _ThreadpoolLimiterDecorator(_ThreadpoolLimiter, ContextDecorator): """Same as _ThreadpoolLimiter but to be used as a decorator""" def __init__(self, controller, *, limits=None, user_api=None): self._limits, self._user_api, self._prefixes = self._check_params( limits, user_api ) self._controller = controller def __enter__(self): # we need to set the limits here and not in the __init__ because we want the # limits to be set when calling the decorated function, not when creating the # decorator. self._original_info = self._controller.info() self._set_threadpool_limits() return self @_format_docstring( USER_APIS=", ".join(f'"{api}"' for api in _ALL_USER_APIS), BLAS_LIBS=", ".join(_ALL_BLAS_LIBRARIES), OPENMP_LIBS=", ".join(_ALL_OPENMP_LIBRARIES), ) class threadpool_limits(_ThreadpoolLimiter): """Change the maximal number of threads that can be used in thread pools. This object can be used either as a callable (the construction of this object limits the number of threads), as a context manager in a `with` block to automatically restore the original state of the controlled libraries when exiting the block, or as a decorator through its `wrap` method. Set the maximal number of threads that can be used in thread pools used in the supported libraries to `limit`. This function works for libraries that are already loaded in the interpreter and can be changed dynamically. This effect is global and impacts the whole Python process. There is no thread level isolation as these libraries do not offer thread-local APIs to configure the number of threads to use in nested parallel calls. Parameters ---------- limits : int, dict, 'sequential_blas_under_openmp' or None (default=None) The maximal number of threads that can be used in thread pools - If int, sets the maximum number of threads to `limits` for each library selected by `user_api`. - If it is a dictionary `{{key: max_threads}}`, this function sets a custom maximum number of threads for each `key` which can be either a `user_api` or a `prefix` for a specific library. - If 'sequential_blas_under_openmp', it will chose the appropriate `limits` and `user_api` parameters for the specific use case of sequential BLAS calls within an OpenMP parallel region. The `user_api` parameter is ignored. - If None, this function does not do anything. user_api : {USER_APIS} or None (default=None) APIs of libraries to limit. Used only if `limits` is an int. - If "blas", it will only limit BLAS supported libraries ({BLAS_LIBS}). - If "openmp", it will only limit OpenMP supported libraries ({OPENMP_LIBS}). Note that it can affect the number of threads used by the BLAS libraries if they rely on OpenMP. - If None, this function will apply to all supported libraries. """ def __init__(self, limits=None, user_api=None): super().__init__(ThreadpoolController(), limits=limits, user_api=user_api) @classmethod def wrap(cls, limits=None, user_api=None): return super().wrap(ThreadpoolController(), limits=limits, user_api=user_api) class ThreadpoolController: """Collection of LibController objects for all loaded supported libraries Attributes ---------- lib_controllers : list of `LibController` objects The list of library controllers of all loaded supported libraries. """ # Cache for libc under POSIX and a few system libraries under Windows. # We use a class level cache instead of an instance level cache because # it's very unlikely that a shared library will be unloaded and reloaded # during the lifetime of a program. _system_libraries = dict() def __init__(self): self.lib_controllers = [] self._load_libraries() self._warn_if_incompatible_openmp() @classmethod def _from_controllers(cls, lib_controllers): new_controller = cls.__new__(cls) new_controller.lib_controllers = lib_controllers return new_controller def info(self): """Return lib_controllers info as a list of dicts""" return [lib_controller.info() for lib_controller in self.lib_controllers] def select(self, **kwargs): """Return a ThreadpoolController containing a subset of its current library controllers It will select all libraries matching at least one pair (key, value) from kwargs where key is an entry of the library info dict (like "user_api", "internal_api", "prefix", ...) and value is the value or a list of acceptable values for that entry. For instance, `ThreadpoolController().select(internal_api=["blis", "openblas"])` will select all library controllers whose internal_api is either "blis" or "openblas". """ for key, vals in kwargs.items(): kwargs[key] = [vals] if not isinstance(vals, list) else vals lib_controllers = [ lib_controller for lib_controller in self.lib_controllers if any( getattr(lib_controller, key, None) in vals for key, vals in kwargs.items() ) ] return ThreadpoolController._from_controllers(lib_controllers) def _get_params_for_sequential_blas_under_openmp(self): """Return appropriate params to use for a sequential BLAS call in an OpenMP loop This function takes into account the unexpected behavior of OpenBLAS with the OpenMP threading layer. """ if self.select( internal_api="openblas", threading_layer="openmp" ).lib_controllers: return {"limits": None, "user_api": None} return {"limits": 1, "user_api": "blas"} @_format_docstring( USER_APIS=", ".join('"{}"'.format(api) for api in _ALL_USER_APIS), BLAS_LIBS=", ".join(_ALL_BLAS_LIBRARIES), OPENMP_LIBS=", ".join(_ALL_OPENMP_LIBRARIES), ) def limit(self, *, limits=None, user_api=None): """Change the maximal number of threads that can be used in thread pools. This function returns an object that can be used either as a callable (the construction of this object limits the number of threads) or as a context manager, in a `with` block to automatically restore the original state of the controlled libraries when exiting the block. Set the maximal number of threads that can be used in thread pools used in the supported libraries to `limits`. This function works for libraries that are already loaded in the interpreter and can be changed dynamically. This effect is global and impacts the whole Python process. There is no thread level isolation as these libraries do not offer thread-local APIs to configure the number of threads to use in nested parallel calls. Parameters ---------- limits : int, dict, 'sequential_blas_under_openmp' or None (default=None) The maximal number of threads that can be used in thread pools - If int, sets the maximum number of threads to `limits` for each library selected by `user_api`. - If it is a dictionary `{{key: max_threads}}`, this function sets a custom maximum number of threads for each `key` which can be either a `user_api` or a `prefix` for a specific library. - If 'sequential_blas_under_openmp', it will chose the appropriate `limits` and `user_api` parameters for the specific use case of sequential BLAS calls within an OpenMP parallel region. The `user_api` parameter is ignored. - If None, this function does not do anything. user_api : {USER_APIS} or None (default=None) APIs of libraries to limit. Used only if `limits` is an int. - If "blas", it will only limit BLAS supported libraries ({BLAS_LIBS}). - If "openmp", it will only limit OpenMP supported libraries ({OPENMP_LIBS}). Note that it can affect the number of threads used by the BLAS libraries if they rely on OpenMP. - If None, this function will apply to all supported libraries. """ return _ThreadpoolLimiter(self, limits=limits, user_api=user_api) @_format_docstring( USER_APIS=", ".join('"{}"'.format(api) for api in _ALL_USER_APIS), BLAS_LIBS=", ".join(_ALL_BLAS_LIBRARIES), OPENMP_LIBS=", ".join(_ALL_OPENMP_LIBRARIES), ) def wrap(self, *, limits=None, user_api=None): """Change the maximal number of threads that can be used in thread pools. This function returns an object that can be used as a decorator. Set the maximal number of threads that can be used in thread pools used in the supported libraries to `limits`. This function works for libraries that are already loaded in the interpreter and can be changed dynamically. Parameters ---------- limits : int, dict or None (default=None) The maximal number of threads that can be used in thread pools - If int, sets the maximum number of threads to `limits` for each library selected by `user_api`. - If it is a dictionary `{{key: max_threads}}`, this function sets a custom maximum number of threads for each `key` which can be either a `user_api` or a `prefix` for a specific library. - If None, this function does not do anything. user_api : {USER_APIS} or None (default=None) APIs of libraries to limit. Used only if `limits` is an int. - If "blas", it will only limit BLAS supported libraries ({BLAS_LIBS}). - If "openmp", it will only limit OpenMP supported libraries ({OPENMP_LIBS}). Note that it can affect the number of threads used by the BLAS libraries if they rely on OpenMP. - If None, this function will apply to all supported libraries. """ return _ThreadpoolLimiter.wrap(self, limits=limits, user_api=user_api) def __len__(self): return len(self.lib_controllers) def _load_libraries(self): """Loop through loaded shared libraries and store the supported ones""" if sys.platform == "darwin": self._find_libraries_with_dyld() elif sys.platform == "win32": self._find_libraries_with_enum_process_module_ex() elif "pyodide" in sys.modules: self._find_libraries_pyodide() else: self._find_libraries_with_dl_iterate_phdr() def _find_libraries_with_dl_iterate_phdr(self): """Loop through loaded libraries and return binders on supported ones This function is expected to work on POSIX system only. This code is adapted from code by Intel developer @anton-malakhov available at https://github.com/IntelPython/smp Copyright (c) 2017, Intel Corporation published under the BSD 3-Clause license """ libc = self._get_libc() if not hasattr(libc, "dl_iterate_phdr"): # pragma: no cover warnings.warn( "Could not find dl_iterate_phdr in the C standard library.", RuntimeWarning, ) return [] # Callback function for `dl_iterate_phdr` which is called for every # library loaded in the current process until it returns 1. def match_library_callback(info, size, data): # Get the path of the current library filepath = info.contents.dlpi_name if filepath: filepath = filepath.decode("utf-8") # Store the library controller if it is supported and selected self._make_controller_from_path(filepath) return 0 c_func_signature = ctypes.CFUNCTYPE( ctypes.c_int, # Return type ctypes.POINTER(_dl_phdr_info), ctypes.c_size_t, ctypes.c_char_p, ) c_match_library_callback = c_func_signature(match_library_callback) data = ctypes.c_char_p(b"") libc.dl_iterate_phdr(c_match_library_callback, data) def _find_libraries_with_dyld(self): """Loop through loaded libraries and return binders on supported ones This function is expected to work on OSX system only """ libc = self._get_libc() if not hasattr(libc, "_dyld_image_count"): # pragma: no cover warnings.warn( "Could not find _dyld_image_count in the C standard library.", RuntimeWarning, ) return [] n_dyld = libc._dyld_image_count() libc._dyld_get_image_name.restype = ctypes.c_char_p for i in range(n_dyld): filepath = ctypes.string_at(libc._dyld_get_image_name(i)) filepath = filepath.decode("utf-8") # Store the library controller if it is supported and selected self._make_controller_from_path(filepath) def _find_libraries_with_enum_process_module_ex(self): """Loop through loaded libraries and return binders on supported ones This function is expected to work on windows system only. This code is adapted from code by Philipp Hagemeister @phihag available at https://stackoverflow.com/questions/17474574 """ from ctypes.wintypes import DWORD, HMODULE, MAX_PATH PROCESS_QUERY_INFORMATION = 0x0400 PROCESS_VM_READ = 0x0010 LIST_LIBRARIES_ALL = 0x03 ps_api = self._get_windll("Psapi") kernel_32 = self._get_windll("kernel32") h_process = kernel_32.OpenProcess( PROCESS_QUERY_INFORMATION | PROCESS_VM_READ, False, os.getpid() ) if not h_process: # pragma: no cover raise OSError(f"Could not open PID {os.getpid()}") try: buf_count = 256 needed = DWORD() # Grow the buffer until it becomes large enough to hold all the # module headers while True: buf = (HMODULE * buf_count)() buf_size = ctypes.sizeof(buf) if not ps_api.EnumProcessModulesEx( h_process, ctypes.byref(buf), buf_size, ctypes.byref(needed), LIST_LIBRARIES_ALL, ): raise OSError("EnumProcessModulesEx failed") if buf_size >= needed.value: break buf_count = needed.value // (buf_size // buf_count) count = needed.value // (buf_size // buf_count) h_modules = map(HMODULE, buf[:count]) # Loop through all the module headers and get the library path buf = ctypes.create_unicode_buffer(MAX_PATH) n_size = DWORD() for h_module in h_modules: # Get the path of the current module if not ps_api.GetModuleFileNameExW( h_process, h_module, ctypes.byref(buf), ctypes.byref(n_size) ): raise OSError("GetModuleFileNameEx failed") filepath = buf.value # Store the library controller if it is supported and selected self._make_controller_from_path(filepath) finally: kernel_32.CloseHandle(h_process) def _find_libraries_pyodide(self): """Pyodide specific implementation for finding loaded libraries. Adapted from suggestion in https://github.com/joblib/threadpoolctl/pull/169#issuecomment-1946696449. One day, we may have a simpler solution. libc dl_iterate_phdr needs to be implemented in Emscripten and exposed in Pyodide, see https://github.com/emscripten-core/emscripten/issues/21354 for more details. """ try: from pyodide_js._module import LDSO except ImportError: warnings.warn( "Unable to import LDSO from pyodide_js._module. This should never " "happen." ) return for filepath in LDSO.loadedLibsByName.as_object_map(): # Some libraries are duplicated by Pyodide and do not exist in the # filesystem, so we first check for the existence of the file. For # more details, see # https://github.com/joblib/threadpoolctl/pull/169#issuecomment-1947946728 if os.path.exists(filepath): self._make_controller_from_path(filepath) def _make_controller_from_path(self, filepath): """Store a library controller if it is supported and selected""" # Required to resolve symlinks filepath = _realpath(filepath) # `lower` required to take account of OpenMP dll case on Windows # (vcomp, VCOMP, Vcomp, ...) filename = os.path.basename(filepath).lower() # Loop through supported libraries to find if this filename corresponds # to a supported one. for controller_class in _ALL_CONTROLLERS: # check if filename matches a supported prefix prefix = self._check_prefix(filename, controller_class.filename_prefixes) # filename does not match any of the prefixes of the candidate # library. move to next library. if prefix is None: continue # workaround for BLAS libraries packaged by conda-forge on windows, which # are all renamed "libblas.dll". We thus have to check to which BLAS # implementation it actually corresponds looking for implementation # specific symbols. if prefix == "libblas": if filename.endswith(".dll"): libblas = ctypes.CDLL(filepath, _RTLD_NOLOAD) if not any( hasattr(libblas, func) for func in controller_class.check_symbols ): continue else: # We ignore libblas on other platforms than windows because there # might be a libblas dso comming with openblas for instance that # can't be used to instantiate a pertinent LibController (many # symbols are missing) and would create confusion by making a # duplicate entry in threadpool_info. continue # filename matches a prefix. Now we check if the library has the symbols we # are looking for. If none of the symbols exists, it's very likely not the # expected library (e.g. a library having a common prefix with one of the # our supported libraries). Otherwise, create and store the library # controller. lib_controller = controller_class( filepath=filepath, prefix=prefix, parent=self ) if filepath in (lib.filepath for lib in self.lib_controllers): # We already have a controller for this library. continue if not hasattr(controller_class, "check_symbols") or any( hasattr(lib_controller.dynlib, func) for func in controller_class.check_symbols ): self.lib_controllers.append(lib_controller) def _check_prefix(self, library_basename, filename_prefixes): """Return the prefix library_basename starts with Return None if none matches. """ for prefix in filename_prefixes: if library_basename.startswith(prefix): return prefix return None def _warn_if_incompatible_openmp(self): """Raise a warning if llvm-OpenMP and intel-OpenMP are both loaded""" prefixes = [lib_controller.prefix for lib_controller in self.lib_controllers] msg = textwrap.dedent( """ Found Intel OpenMP ('libiomp') and LLVM OpenMP ('libomp') loaded at the same time. Both libraries are known to be incompatible and this can cause random crashes or deadlocks on Linux when loaded in the same Python program. Using threadpoolctl may cause crashes or deadlocks. For more information and possible workarounds, please see https://github.com/joblib/threadpoolctl/blob/master/multiple_openmp.md """ ) if "libomp" in prefixes and "libiomp" in prefixes: warnings.warn(msg, RuntimeWarning) @classmethod def _get_libc(cls): """Load the lib-C for unix systems.""" libc = cls._system_libraries.get("libc") if libc is None: # Remark: If libc is statically linked or if Python is linked against an # alternative implementation of libc like musl, find_library will return # None and CDLL will load the main program itself which should contain the # libc symbols. We still name it libc for convenience. # If the main program does not contain the libc symbols, it's ok because # we check their presence later anyway. libc = ctypes.CDLL(find_library("c"), mode=_RTLD_NOLOAD) cls._system_libraries["libc"] = libc return libc @classmethod def _get_windll(cls, dll_name): """Load a windows DLL""" dll = cls._system_libraries.get(dll_name) if dll is None: dll = ctypes.WinDLL(f"{dll_name}.dll") cls._system_libraries[dll_name] = dll return dll def _main(): """Commandline interface to display thread-pool information and exit.""" import argparse import importlib import json import sys parser = argparse.ArgumentParser( usage="python -m threadpoolctl -i numpy scipy.linalg xgboost", description="Display thread-pool information and exit.", ) parser.add_argument( "-i", "--import", dest="modules", nargs="*", default=(), help="Python modules to import before introspecting thread-pools.", ) parser.add_argument( "-c", "--command", help="a Python statement to execute before introspecting thread-pools.", ) options = parser.parse_args(sys.argv[1:]) for module in options.modules: try: importlib.import_module(module, package=None) except ImportError: print("WARNING: could not import", module, file=sys.stderr) if options.command: exec(options.command) print(json.dumps(threadpool_info(), indent=2)) if __name__ == "__main__": _main()