On 12/4/19, Song, Ruiling <ruiling.s...@intel.com> wrote: >> -----Original Message----- >> From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of >> chen >> Sent: Wednesday, December 4, 2019 9:36 AM >> To: FFmpeg development discussions and patches <ffmpeg- >> de...@ffmpeg.org> >> Subject: Re: [FFmpeg-devel] [PATCH 3/3] avfilter/vf_convolution: add X86 >> SIMD for filter_column() >> >> >> >> At 2019-12-04 08:59:08, "Song, Ruiling" <ruiling.s...@intel.com> wrote: >> >> -----Original Message----- >> >> From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of >> >> chen >> >> Sent: Tuesday, December 3, 2019 4:59 PM >> >> To: FFmpeg development discussions and patches <ffmpeg- >> >> de...@ffmpeg.org> >> >> Subject: Re: [FFmpeg-devel] [PATCH 3/3] avfilter/vf_convolution: add >> >> X86 >> >> SIMD for filter_column() >> >> >> >> comments inline in code >> >> >> >> >> >> At 2019-12-03 15:52:07, xuju...@sjtu.edu.cn wrote: >> >> >From: Xu Jun <xuju...@sjtu.edu.cn> >> >[...] >> >> >+ >> >> >+ cvtdq2ps m4, m4 >> >> >+ mulps m4, m0 ; sum *= rdiv >> >> >+ addps m4, m1 ; sum += bias >> >> >> >> >+ addps m4, m5 ; sum += 0.5 >> >> I don't know how about precision mismatch if we pre-compute (bias+0.5) >> >> >I think it is hard to prove it is safe to do pre-compute. >> Agree, I also worried precision issue since float operator is execute >> order >> dependent. >> How about ROUNDPS? > Seems no exactly match. >> >> >> > >> >> >> >> >> >> >+ cvttps2dq m4, m4 >> >> >+ packssdw m4, m4 >> >> >+ packuswb m4, m4 >> >> >+ movss [dstq + dst_offq], m4 >> >> >+ add c_offq, mmsize/4 >> >> >+ add dst_offq, mmsize/4 >> >> >+ >> >> >+ add off16q, mmsize/4 >> >> >+ cmp off16q, widthq >> >> >+ jl .loop16 >> >> >+ >> >> >+ add widthq, rq >> >> >+ cmp off16q, widthq >> >> >+ jge .paraend >> >> >+ >> >> >> >> >+ .loopr: >> >> no idea about this loop, if we can read beyond, we can reuse above >> >> SIMD >> >> code >> >Reuse above SIMD code may write to the memory that does not belong to >> this slice-thread. >> >> >IMO, the code to handle remainder columns is still necessary. >> >> >> Depends on algorithm & size, >> For example width=23 >> Process #0 [0:15] >> Process #1 [7:22] >> Both of them is multiple of 16 > Sounds interesting. But FFmpeg does not do like this now. > One question is will this get a penalty for writing to same address of > memory (both are writing to 7-15) from different threads?
Yes, and even bad results may happen. > >> >> _______________________________________________ >> ffmpeg-devel mailing list >> ffmpeg-devel@ffmpeg.org >> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> >> To unsubscribe, visit link above, or email >> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".