python/pyarrow/_config.pyx

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# with the License.  You may obtain a copy of the License at
#
#   http://www.apache.org/licenses/LICENSE-2.0
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# cython: profile=False
# distutils: language = c++
# cython: embedsignature = True

import numpy as np
import multiprocessing
import os

cdef extern from 'arrow/python/init.h':
    int arrow_init_numpy() except -1

cdef extern from 'arrow/python/config.h' namespace 'arrow::py':
    void set_numpy_nan(object o)

arrow_init_numpy()

set_numpy_nan(np.nan)

cdef int CPU_COUNT = int(
    os.environ.get('OMP_NUM_THREADS',
                   max(multiprocessing.cpu_count() // 2, 1)))


def cpu_count():
    """
    Returns
    -------
    count : Number of CPUs to use by default in parallel operations. Default is
      max(1, multiprocessing.cpu_count() / 2), but can be overridden by the
      OMP_NUM_THREADS environment variable. For the default, we divide the CPU
      count by 2 because most modern computers have hyperthreading turned on,
      so doubling the CPU count beyond the number of physical cores does not
      help.
    """
    return CPU_COUNT


def set_cpu_count(count):
    global CPU_COUNT
    CPU_COUNT = max(int(count), 1)