Is this make sence? Dynamic assembler for python

[MRAB]

David Cournapeau wrote:
> On Mon, Jun 21, 2010 at 12:34 PM, Steven D'Aprano
> <steve-REMOVE-THIS at cybersource.com.au> wrote:
>> On Sun, 20 Jun 2010 22:45:14 +0100, Rhodri James wrote:
>>
>>> Mixing Python and assembler is a bizarre thing to want to do in general,
>>> but...
>>>
>>> On Sun, 20 Jun 2010 01:52:15 +0100, Steven D'Aprano
>>> <steve at remove-this-cybersource.com.au> wrote:
>>>
>>>> (3) Modern C compilers can produce better (faster, more efficient)
>>>> machine code than the best assembly code written by hand.
>>> No.  Modern C compilers often produce very good machine code, but the
>>> best hand-written assembly code will be better.  I can usually write
>>> *very* marginally better code than GCC achieves at work, though 99% of
>>> the time I don't because it would be a maintenance nightmare.
>>
>> Not that I don't believe you, but that is an extraordinary claim that
>> would require more evidence than just "Hey, some guy on the Internet
>> reckons his assembly code can regularly out-perform optimizing C
>> compilers" before I will change my opinion *wink*
> 
> No, it is not extraordinary claim, I would actually think it is common
> knowledge. For performance sensitive, extremely well constraints
> algorithm, ASM easily beats general C compilers. Most optimized
> numerical libraries rely quite heavily on ASM to get significant speed
> up (Atlas, FFTW, MKL). C has actually a few majors aspects which makes
> some optimizations very hard to do - things like pointer aliasing, for
> example, where the compiler has to be quite pessimistic in general.
> 
> Also, the fact that current compilers can generate code which is
> significantly faster than they used to a few years ago *on the exact
> same C code* show that it is not that hard to beat C compilers. They
> manage to do it by themselves :)
> 
A human can write better assembly code than a compiler, but would take a
much longer, and usually for not much gain, so it's usually a waste of
time (premature optimisation, and all that).