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"""Helpers for OpenMP support during the build."""
# This code is adapted for a large part from the astropy openmp helpers, which
# can be found at: https://github.com/astropy/extension-helpers/blob/master/extension_helpers/_openmp_helpers.py # noqa
import os
import sys
import textwrap
import warnings
from .pre_build_helpers import compile_test_program
def get_openmp_flag():
if sys.platform == "win32":
return ["/openmp"]
elif sys.platform == "darwin" and "openmp" in os.getenv("CPPFLAGS", ""):
# -fopenmp can't be passed as compile flag when using Apple-clang.
# OpenMP support has to be enabled during preprocessing.
#
# For example, our macOS wheel build jobs use the following environment
# variables to build with Apple-clang and the brew installed "libomp":
#
# export CPPFLAGS="$CPPFLAGS -Xpreprocessor -fopenmp"
# export CFLAGS="$CFLAGS -I/usr/local/opt/libomp/include"
# export CXXFLAGS="$CXXFLAGS -I/usr/local/opt/libomp/include"
# export LDFLAGS="$LDFLAGS -Wl,-rpath,/usr/local/opt/libomp/lib
# -L/usr/local/opt/libomp/lib -lomp"
return []
# Default flag for GCC and clang:
return ["-fopenmp"]
def check_openmp_support():
"""Check whether OpenMP test code can be compiled and run"""
if "PYODIDE_PACKAGE_ABI" in os.environ:
# Pyodide doesn't support OpenMP
return False
code = textwrap.dedent("""\
#include <omp.h>
#include <stdio.h>
int main(void) {
#pragma omp parallel
printf("nthreads=%d\\n", omp_get_num_threads());
return 0;
}
""")
extra_preargs = os.getenv("LDFLAGS", None)
if extra_preargs is not None:
extra_preargs = extra_preargs.strip().split(" ")
# FIXME: temporary fix to link against system libraries on linux
# "-Wl,--sysroot=/" should be removed
extra_preargs = [
flag
for flag in extra_preargs
if flag.startswith(("-L", "-Wl,-rpath", "-l", "-Wl,--sysroot=/"))
]
extra_postargs = get_openmp_flag()
openmp_exception = None
try:
output = compile_test_program(
code, extra_preargs=extra_preargs, extra_postargs=extra_postargs
)
if output and "nthreads=" in output[0]:
nthreads = int(output[0].strip().split("=")[1])
openmp_supported = len(output) == nthreads
elif "PYTHON_CROSSENV" in os.environ:
# Since we can't run the test program when cross-compiling
# assume that openmp is supported if the program can be
# compiled.
openmp_supported = True
else:
openmp_supported = False
except Exception as exception:
# We could be more specific and only catch: CompileError, LinkError,
# and subprocess.CalledProcessError.
# setuptools introduced CompileError and LinkError, but that requires
# version 61.1. Even the latest version of Ubuntu (22.04LTS) only
# ships with 59.6. So for now we catch all exceptions and reraise a
# generic exception with the original error message instead:
openmp_supported = False
openmp_exception = exception
if not openmp_supported:
if os.getenv("SKLEARN_FAIL_NO_OPENMP"):
raise Exception(
"Failed to build scikit-learn with OpenMP support"
) from openmp_exception
else:
message = textwrap.dedent("""
***********
* WARNING *
***********
It seems that scikit-learn cannot be built with OpenMP.
- Make sure you have followed the installation instructions:
https://scikit-learn.org/dev/developers/advanced_installation.html
- If your compiler supports OpenMP but you still see this
message, please submit a bug report at:
https://github.com/scikit-learn/scikit-learn/issues
- The build will continue with OpenMP-based parallelism
disabled. Note however that some estimators will run in
sequential mode instead of leveraging thread-based
parallelism.
***
""")
warnings.warn(message)
return openmp_supported
|
