[x265] [PATCH 1/2] weight prediction: use sqrtf

[Rafaël Carré]

On 03/05/14 18:06, Steve Borho wrote:
> On Wed, Mar 5, 2014 at 4:38 AM, Rafaël Carré <funman at videolan.org> wrote:
>> ---
>>  source/encoder/weightPrediction.cpp | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/source/encoder/weightPrediction.cpp b/source/encoder/weightPrediction.cpp
>> index c04361a..c0710fd 100644
>> --- a/source/encoder/weightPrediction.cpp
>> +++ b/source/encoder/weightPrediction.cpp
>> @@ -203,7 +203,7 @@ bool WeightPrediction::checkDenom(int denom)
>>                  uint64_t fencVar = fenc->wp_ssd[yuv] + !ref->wp_ssd[yuv];
>>                  uint64_t refVar  = ref->wp_ssd[yuv] + !ref->wp_ssd[yuv];
>>                  if (fencVar && refVar)
>> -                    guessScale[yuv] = Clip3(-2.f, 1.8f, std::sqrt((float)fencVar / refVar));
>> +                    guessScale[yuv] = Clip3(-2.f, 1.8f, sqrtf((float)fencVar / refVar));
> 
> Is something wrong with std::sqrt?

I got:
x265/source/encoder/weightPrediction.cpp:206:57: error: 'sqrt' is not a
member of 'std'

With g++ 4.8.2

Full command line is :

cd /home/fun/x265/source/encoder && /usr/bin/c++   -DHAVE_INT_TYPES_H=1
-DHIGH_BIT_DEPTH=0 -DLOG_CU_STATISTICS=0 -DX265_ARCH_X86=1 -DX86_64=1
-O2 -g -DNDEBUG -I/home/fun/x265/source/. -I/home/fun/x265/source/Lib
-I/home/fun/x265/source/common -I/home/fun/x265/source/encoder
-I/home/fun/x265/source    -Wall -Wextra -Wshadow -ffast-math
-mstackrealign -fPIC -o CMakeFiles/encoder.dir/weightPrediction.cpp.o -c
/home/fun/x265/source/encoder/weightPrediction.cpp

Perhaps I am missing a -stdc++=something that was added later?

> This line recently caught my attention; I could not figure out why the
> output of sqrt() was being clipped to a negative base number, or why
> it was clipped on top either, for that matter.
>