[Cython] Utilities, cython.h, libcython

[mark florisson]

On 6 October 2011 21:56, Vitja Makarov <vitja.makarov at gmail.com> wrote:
> 2011/10/6 mark florisson <markflorisson88 at gmail.com>:
>> On 6 October 2011 07:46, Stefan Behnel <stefan_ml at behnel.de> wrote:
>>> mark florisson, 05.10.2011 15:53:
>>>>
>>>> On 5 October 2011 08:16, Stefan Behnel wrote:
>>>>>
>>>>> mark florisson, 04.10.2011 23:19:
>>>>>>
>>>>>> Another issue is that Cython compile time is increasing with the
>>>>>> addition of control flow and cython utilities. If you use fused types
>>>>>> you're also going to combinatorially add more compile time.
>>>>>
>>>>> I don't see that locally - a compiled Cython is hugely fast for me. In
>>>>> comparison, the C compiler literally takes ages to compile the result. An
>>>>> external shared library may or may not help with both - in particular, it
>>>>> is
>>>>> not clear to me what makes the C compiler slow. If the compile time is
>>>>> dominated by the number of inlined functions (which is not unlikely), a
>>>>> shared library + header file will not make a difference.
>>>>
>>>> Have you tried with the memoryviews merged?
>>>
>>> No. I didn't expect the difference to be quite that large.
>>>
>>>
>>>> e.g. if I have this code:
>>>>
>>>> from libc.stdlib cimport malloc
>>>> cdef int[:] slice =<int[:10]>  <int *>  malloc(sizeof(int) * 10)
>>>>
>>>> [0] [14:45] ~  ➤ time cython test.pyx
>>>> cython test.pyx  2.61s user 0.08s system 99% cpu 2.695 total
>>>> [0] [14:45] ~  ➤ time zsh compile
>>>> zsh compile  1.88s user 0.06s system 99% cpu 1.946 total
>>>>
>>>> where 'compile' is the script that invoked the same gcc command
>>>> distutils uses.  As you can see it took more than 2.5 seconds to
>>>> compile this code (simply because the memoryview utilities get
>>>> included).
>>>
>>> Ok, that hints at serious performance problems. Could you profile it to see
>>> where the issues are? Is it more that the code is loaded from an external
>>> file? Or the fact that more utility code is parsed than necessary?
>>
>> I haven't profiled it yet (I'll do that), but I'm fairly sure it's the
>> parsing of Cython utility files (not the loading). Maybe Tempita also
>> adds to the overhead, I'll find out.
>>
>
> Compiling this regex gives 5ms instead of 10ms on my machine
>
> https://github.com/cython/cython/blob/master/Cython/Compiler/Code.py#L85
>
> And on your example gives 3% speedup
>

Sorry, which code gets you 10ms? Also, is this about loading + regex
matching, or just about compiling the pattern?

In any case, libcython would solve these issues. Profiling will still
be useful though.

>>> It's certainly not obvious why the inclusion of static code, even from an
>>> external file, should make any difference.
>>>
>>> That being said, it's not we were lacking the infrastructure for making
>>> Python code run faster ...
>>>
>>
>> Heh, indeed. In this case I think caching will solve all our problems.
>>
>>>>>> I'm sure
>>>>>> this came up earlier, but I really think we should have a libcython
>>>>>> and a cython.h. libcython (a shared library) should contain any common
>>>>>> Cython-specific code not meant to be inlined, and cython.h any types,
>>>>>> macros and inline functions etc.
>>>>>
>>>>> This has a couple of implications though. In order to support this on the
>>>>> user side, we have to build one shared library per installed package in
>>>>> order to avoid any Cython versioning issues. Just installing a versioned
>>>>> "libcython_x.y.z.so" globally isn't enough, especially during
>>>>> development,
>>>>> but also at deployment time. Different packages may use different CFLAGS
>>>>> or
>>>>> Cython options, which may have an impact on the result. Encoding all
>>>>> possible factors in the file name will be cumbersome and may mean that we
>>>>> still end up with a number of installed Cython libraries that correlates
>>>>> with the number of installed Cython based packages.
>>>>
>>>> Hm, I think the CFLAGS are important so long as they are compatible
>>>> with Python. When the user compiles a Cython extension module with
>>>> extra CFLAGS, this doesn't affect libpython. Similarly, the Cython
>>>> utilities are really not the user's responsibility, so libcython
>>>> doesn't need to be compiled with the same flags as the extension
>>>> module. If still wanted, the user could either recompile python with
>>>> different CFLAGS (which means libcython will get those as well), or
>>>> not use libcython at all. CFLAGS should really only pertain to user
>>>> code, not to the Cython library, which the user shouldn't be concerned
>>>> about.
>>>
>>> Well, it's either the user or the OS distribution that installs (and
>>> potentially builds) the libraries. That already makes it two responsible
>>> entities for many systems that have to agree on what gets installed in what
>>> way. I'm just saying, don't underestimate the details in world wide
>>> deployments.
>>>
>
>
>
> --
> vitja.
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