python - cython错误无法分配给外部并行 block 的私有(private)

Question

我试图在 SO 和 Cython 用户论坛上找到此错误的解决方案，但找不到答案。当我测试文档 Cython 0.23.1 documentation 中提供的完全相同的并行性示例时，然后我收到下面附加的错误。我缺少什么？应该如何实现？任何帮助表示赞赏。提前致谢

这是 cython 文档中的代码

from cython.parallel import parallel, prange
from libc.stdlib cimport abort, malloc, free

cdef Py_ssize_t idx, i, n = 100
cdef int * local_buf
cdef size_t size = 10
with nogil, parallel():
    local_buf = <int *> malloc(sizeof(int) * size)
if local_buf == NULL:
    abort()

# populate our local buffer in a sequential loop
for i in xrange(size):
    local_buf[i] = i * 2

# share the work using the thread-local buffer(s)
for i in prange(n, schedule='guided'):
    func(local_buf)

free(local_buf)

# I just simply added this to test it
cdef void func(int* local_buf) nogil:
cdef int i=0
return

这是错误

'''
Compiling thread_local.pyx because it changed.
[1/1] Cythonizing thread_local.pyx

Error compiling Cython file:
------------------------------------------------------------
# populate our local buffer in a sequential loop
for i in xrange(size):
    local_buf[i] = i * 2

# share the work using the thread-local buffer(s)
for i in prange(n, schedule='guided'):
     ^
------------------------------------------------------------

thread_local.pyx:19:10: Cannot assign to private of outer parallel block
Traceback (most recent call last):
 File "setup.py", line 28, in <module>
 ext_modules = cythonize(extensions),)
 File "/apps/anaconda/lib/python2.7/site-  packages/Cython/Build/Dependencies.py", line 877, in cythonize
cythonize_one(*args)
File "/apps/anaconda/lib/python2.7/site-     packages/Cython/Build/Dependencies.py", line 997, in cythonize_one
raise CompileError(None, pyx_file)
Cython.Compiler.Errors.CompileError: thread_local.pyx

Answer 1

感谢 DavidW，他的猜测是正确的。我不太清楚为什么，但似乎您不能在 with nogil, parallel(): block 内的两个 for 循环中重用相同的变量(在本例中为 i ) 。我猜作者的意图是为两个 for 循环使用单独的变量，因为我看到定义了另一个变量 idx，但未使用。我希望他们纠正这个误导性的例子。

from cython.parallel import parallel, prange
from libc.stdlib cimport abort, malloc, free

cdef Py_ssize_t idx, i, n = 100
cdef int * local_buf
cdef size_t size = 10

with nogil, parallel():
    local_buf = <int *> malloc(sizeof(int) * size)
    if local_buf == NULL:
        abort()

# populate our local buffer in a sequential loop
    for i in xrange(size):
        local_buf[i] = i * 2

# share the work using the thread-local buffer(s)
    for idx in prange(n, schedule='guided'):
        func(local_buf)

    free(local_buf)