Doom9's Forum - View Single Post - Older compiler versions produce faster code?

jpsdr · 27th February 2020, 23:11

A little while ago, i've made the following encode speed test, comparing gcc with mcf, winthread or posix thread model, on the 9.2.1 version. The posix was the one provided with msys2, the winthread version here and the mcf version here.
mcf was faster than winthread which was faster than posix. But if was each time around 3 minutes for an 2 hours encode.
The x264 was compiled with the posix thread option with the posix gcc, and with the win32 thread option for the winthread and mcf gcc.

This post made me make a little test, comparing 9.2.1 mcf gcc with 5.5.0 and 4.9.4 winthread gcc (from the links i provided).
x264 was compiled with the win32 thread option (on configure), and gcc had AVX2 option and Broadwell tuning option, targeting x64.
I've encoded a 3000 frames small video, encoding time results are :
GCC 4.9.4 : 11m45s
GCC 5.5.0 : 11m44s
GCC 9.2.1 : 11m43s
So... very similar results...

Edit : forget to tell, build was also fprofiled. Test was under Windows 7 x64.

27th February 2020, 23:11	#8 \| Link
jpsdr Registered User Join Date: Oct 2002 Location: France Posts: 2,316	A little while ago, i've made the following encode speed test, comparing gcc with mcf, winthread or posix thread model, on the 9.2.1 version. The posix was the one provided with msys2, the winthread version here and the mcf version here. mcf was faster than winthread which was faster than posix. But if was each time around 3 minutes for an 2 hours encode. The x264 was compiled with the posix thread option with the posix gcc, and with the win32 thread option for the winthread and mcf gcc. This post made me make a little test, comparing 9.2.1 mcf gcc with 5.5.0 and 4.9.4 winthread gcc (from the links i provided). x264 was compiled with the win32 thread option (on configure), and gcc had AVX2 option and Broadwell tuning option, targeting x64. I've encoded a 3000 frames small video, encoding time results are : GCC 4.9.4 : 11m45s GCC 5.5.0 : 11m44s GCC 9.2.1 : 11m43s So... very similar results... Edit : forget to tell, build was also fprofiled. Test was under Windows 7 x64. __________________ My github. Last edited by jpsdr; 28th February 2020 at 11:07.