如何在cython中正确使用多线程？

Question

我有一个包含 2 个嵌套 for 循环的代码，想用多线程运行它，看看它是否运行得更快？这是我的代码：

import cython
import numpy as np
from cython.parallel import prange

@cython.boundscheck(False)
@cython.wraparound(False)

cpdef int test_speed(unsigned char[:, :] Rint, unsigned char[:, :] Gint, unsigned char[:, :] Bint, unsigned char[:, :] table):
    cdef unsigned char[:, :] R_ch_new=np.zeros((1024, 1024), dtype="uint8")
    cdef unsigned char[:, :] B_ch_new=np.zeros((1024, 1024), dtype="uint8")
    cdef unsigned char[:, :] G_ch_new=np.zeros((1024, 1024), dtype="uint8")
    cdef int i, j
    for i in range(1024):
           for j in range(1024):
               # r = np.round(Rint[i,j])
               R_ch_new[i,j]=table[0, Rint[i,j]]
               # s = np.round(Gint[i,j])
               G_ch_new[i,j]=table[0, Gint[i,j]]
               # t = np.round(Bint[i,j])
               B_ch_new[i,j]=table[0, Bint[i,j]]
    return 1

我尝试了这段代码，没有注意到任何加速，还检查了进程线程，只有 1 个线程忙于 12-14%，所以这是正常工作还是我做错了什么？

import cython
import numpy as np
from cython.parallel import prange


@cython.boundscheck(False)
@cython.wraparound(False)
cpdef int test_speed(unsigned char[:, :] Rint, unsigned char[:, :] Gint, unsigned char[:, :] Bint, unsigned char[:, :] table):
    cdef unsigned char[:, :] R_ch_new=np.zeros((1024, 1024), dtype='uint8')
    cdef unsigned char[:, :] B_ch_new=np.zeros((1024, 1024), dtype='uint8')
    cdef unsigned char[:, :] G_ch_new=np.zeros((1024, 1024), dtype='uint8')

    cdef int i, j

    for i in prange(1024, nogil=True):
           for j in range(1024):
               # r = np.round(Rint[i,j])
               R_ch_new[i,j]=table[0, Rint[i,j]]
               # s = np.round(Gint[i,j])
               G_ch_new[i,j]=table[0, Gint[i,j]]
               # t = np.round(Bint[i,j])
               B_ch_new[i,j]=table[0, Bint[i,j]]
    return 1

这就是我测试速度的方式：

import time

import numpy as np
from testspeed1 import test_speed
table=np.zeros((1, 256), dtype='uint8')
Rint=np.zeros((1024, 1024), dtype='uint8')
Gint=np.zeros((1024, 1024), dtype='uint8')
Bint=np.zeros((1024, 1024), dtype='uint8')

for i in range(1024):
    for j in range(1024):
        Rint[i, j] = np.random.randint(0, 255)
        Gint[i, j] = np.random.randint(0, 255)
        Bint[i, j] = np.random.randint(0, 255)

for i in range(256):
    table[0, i] = np.random.randint(0, 255)

start = time.time()
result = test_speed(Rint, Gint, Bint, table)
end = time.time()
print('duration : ', str(end - start))

***更新： 我使用这个 setup.py :

from distutils.core import setup

import numpy
from Cython.Build import cythonize
from distutils.extension import Extension
from Cython.Distutils import build_ext

ext_modules = [
    Extension("testspeed1",
              ["testspeed1.pyx"],
              extra_compile_args=['-fopenmp'],

              include_dirs=[numpy.get_include()]
              )
]

setup(
    name="testspeed1",
    ext_modules=cythonize(ext_modules),
    include_dirs=[numpy.get_include()]
)

并使用以下命令运行：

python setup.py build_ext --inplace

Answer 1

一般来说，我会在安装文件中添加它：

if sys.platform.startswith("win"):
     openmp_arg = '-openmp'
     opt_compiler = '/O2'
else:
     openmp_arg = '-fopenmp'
     opt_compiler = '-O3'

ext_modules = [Extension("name",
                     ["source to pyx"],
                     extra_compile_args=[openmp_arg, opt_compiler],
                     extra_link_args=[openmp_arg] if '-f' in openmp_arg else [])]

干杯