如何在Cython中使用128位整数 [英] How to use 128 bit integers in Cython

问题描述

在我的64位计算机上， long long 类型具有64位.

On my 64 bit computer the long long type has 64 bits.

print(sizeof(long long))
# prints 8

我需要使用128位整数，幸运的是 GCC支持这些.如何在Cython中使用它们?

I need to use 128 bit integers and luckily GCC supports these. How can I use these within Cython?

以下内容无效.编译仅包含

The following doesn't work. Compiling foo.pyx containing just

cdef __int128_t x = 0

收益

$ cython foo.pyx 

Error compiling Cython file:
------------------------------------------------------------
...

cdef __int128_t x = 0
    ^
------------------------------------------------------------

foo.pyx:2:5: '__int128_t' is not a type identifier

推荐答案

这不再是解决方法，这是正确的方法.另请参阅@IanH的答案.

this is NOT a workaround anymore, this is the right way to do it. Refer also to @IanH's answer.

现在，您遇到的问题是 cython 无法识别您的类型，而 gcc 可以识别您的类型.因此，我们可以尝试欺骗 cython .

Now, the problem you have is that cython does not recognize your type, while gcc does. So we can try to trick cython.

文件 helloworld.pyx :

cdef extern from "header_int128.h":
    # this is WRONG, as this would be a int64. it is here
    # just to let cython pass the first step, which is generating
    # the .c file.
    ctypedef unsigned long long int128

print "hello world"

cpdef int foo():
    cdef int128 foo = 4
    return 32

文件 header_int128.h :

typedef __int128_t int128;

文件 setup.py :

from distutils.core import setup
from Cython.Build import cythonize

setup(ext_modules = cythonize("helloworld.pyx"))

现在，在我的机器上，当我运行 python setup.py build_ext --inplace 时，第一步通过了，并生成了 helloworld.c 文件，并且然后 gcc 编译也会通过.

Now, on my machine, when I run python setup.py build_ext --inplace, the first step passes, and the file helloworld.c is generated, and then the gcc compilation passes as well.

现在，如果打开文件 helloworld.c ，则可以检查变量 foo 实际上是否声明为 int128 .

Now if you open the file helloworld.c, you can check that your variable foo is actually declared as an int128.

使用此替代方法要非常小心.特别是，例如，如果您将 int128 分配给 int64 ，则cython不需要强制转换C代码，因为在该过程的该步骤实际上并没有区分它们.

Be very careful with using this workaround. In particular, it can happen that cython will not require a cast in the C code if you assign an int128 to a int64 for example, because at that step of the process it actually does not distinguish between them.

这篇关于如何在Cython中使用128位整数的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！