Slow performance compared to C++, ideas?

Manu turkeyman at gmail.com
Sat Jun 1 23:33:34 PDT 2013


On 2 June 2013 01:19, Paulo Pinto <pjmlp at progtools.org> wrote:

> Am 01.06.2013 16:24, schrieb Benjamin Thaut:
>
>  Am 01.06.2013 01:30, schrieb Manu:
>>
>>> On 1 June 2013 09:15, bearophile <bearophileHUGS at lycos.com
>>> <mailto:bearophileHUGS at lycos.**com <bearophileHUGS at lycos.com>>> wrote:
>>>
>>>     Manu:
>>>
>>>         On 1 June 2013 01:12, bearophile <bearophileHUGS at lycos.com
>>>         <mailto:bearophileHUGS at lycos.**com <bearophileHUGS at lycos.com>>>
>>> wrote:
>>>
>>>             Manu:
>>>
>>>
>>>               Frankly, this is a textbook example of why STL is the
>>>             spawn of satan. For
>>>
>>>                 some reason people are TAUGHT that it's reasonable to
>>>                 write code like
>>>                 this.
>>>
>>>
>>>             There are many kinds of D code, not everything is a high
>>>             performance
>>>             ray-tracer or 3D game. So I'm sure there are many many
>>>             situations where
>>>             using the C++ STL is more than enough. As most tools, you
>>>             need to know
>>>             where and when to use them. So it's not a Satan-spawn :-)
>>>
>>>
>>>         So why are we having this conversation at all then if faster
>>>         isn't better in this instance?
>>>
>>>
>>>     Faster is better in this instance.
>>>     What's wrong is your thinking that the STL as the spawn of Satan in
>>>     general.
>>>
>>>
>>> Ah, but that's because it is ;)
>>> Rule of thumb: never use STL in tight loops. problem solved (well,
>>> mostly)...
>>>
>>
>> I have to agree here. Whenever you have a codebase that has to work on 9
>> platforms and 6 compilers the S in STL vanishes. Also the
>> implementations are so varying in quality that you might get really good
>> performance on one platform but really bad on another. It seems like
>> everyone in the games industry avoids STL like the plague.
>>
>> Kind Regards
>> Benjamin Thaut
>>
>
> I used to have that experience even with C, when I started using it around
> 1994. C++ was even worse between CFront, ARM and ongoing standardization
> work.
>
> As for STL, I can assure that HPC guys are huge fans of STL and Boost.
>

The funny thing about HPC guys though, at least in my experience (a bunch
of researchers from Cambridge who I often give _basic_ optimisation tips),
is they don't write/run 'high performance software', they're actually
pretty terrible programmers and have a tendency to write really low
performing software, but run it on super high performance computers, and
then call the experience high performance computing...
It bends my mind to see them demand an order of magnitude more computing
power to run an algorithm that's hamstrung by poor choices of containers or
algorithms that probably cost them an order of magnitude in performance ;)
And then the Universities take their demands seriously and deliver them
more hardware! O_O

At least when I did my traineeship at CERN (2003-2004) that was the case.
>

I hope CERN has better software engineers than Cambridge University ;)
Most of these guys are mathematicians and physicists first, and programmers
second.
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