Hi Mattias,
patch is ok. I am still a bit curious to learn about that high delay
caused by getenv ().
Kai
2015-04-01 5:35 GMT+02:00 Dongsheng Song <dongsheng.s...@gmail.com>:
> Hi Mattias,
>
> Could you share your micro benchmark data ?
>
> In my testing, getenv() is very fast.
>
> *) unset PRINTF_EXPONENT_DIGITS
>
> preheat 10000 times, then perform 1000000 times (use 4.67777 seconds)
> getenv cost: 4.67777 us
>
> *) set PRINTF_EXPONENT_DIGITS=3
> preheat 10000 times, then perform 1000000 times (use 3.41991 seconds)
> getenv: 3.41991 us
>
> My CPU is Core2 E6550 at 2.33 GHz.
>
> On Wed, Apr 1, 2015 at 10:26 AM, Dongsheng Song <dongsheng.s...@gmail.com>
> wrote:
>>
>> Cache getenv() looks a good idea !
>> Patch is OK for me.
>>
>> On Wed, Apr 1, 2015 at 4:16 AM, Mattias Engdegård <matti...@acm.org>
>> wrote:
>>>
>>> The functions in the __mingw_printf family are very slow because of the
>>> getenv("PRINTF_EXPONENT_DIGITS") call that is made every time, even when
>>> that information isn't actually needed.
>>>
>>> Please consider this patch. It only calls getenv once, caching the result
>>> (as is traditionally done in libraries that use environment variables this
>>> way). It also only computes the minimum exponent digits when actually
>>> needed, at most once per format call.
>>>
>>> With this patch, __mingw_sprintf(buf, "x") goes from being several orders
>>> of magnitude slower than the MSVCRT sprintf, to about 66% faster. You don't
>>> see this kind of improvement every day.
>>
>>
>
>
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