Re:Apple announces it will switch to its own processors for ...
by Veedrac on Monday June 22, 2020 @09:08PM
(#23608899)
The official results from spec.org have a bunch of cheating, eg. exploiting undefined behaviour to run a benchmark improperly. AnandTech uses a consistent compiler (Clang, not ICC) without settings to exploit this, hence the divergence.
Andrei mentions this here: https://www.realworldtech.com/forum/?threadid=187314&curpost...
Re:Apple announces it will switch to its own processors for ...
by KMag on Tuesday June 23, 2020 @02:30AM
(#23610516)
When I started at Google, I sat next to a guy who used to write compilers for DEC and Intel. I asked him, given the huge amount Google spends on hardware and electricity, if he thought that switching to ICC was worth while. His answer was basically that ICC is tuned to maximally exploit undefined behavior for marketing purposes and he wouldn't want to use it in production, at least without heavily tweaking flags to disable some optimizations. ICC gets most of its speed advantages by enabling optimizations that are present in GCC/Clang, but deemed too dangerous to turn on by default.
Re:Apple announces it will switch to its own processors for ...
by fock on Tuesday June 23, 2020 @03:17AM
(#23610789)
clang with "-Ofast"; I really wonder, which other options are there?! And imho this just doesn't explain the 200% difference?
And some other things which are bugging me:
- can you only optimize for A53 on Android with the big.LITTLE-configurations (they do!)?
- so they cross-compiled an AMD64-producing gcc 3.2 with Xcode 10 on MacOS-X for ARM? impressive.
I guess AMD is fine for me (as is my old Intel-notebook) and I'll just wait for POVray, GROMACS and Co.
EDIT: And well, I noticed, supposedly Anandtech ran SPECint2006 on the A13 (and numerous other chips) - they ran it with WSL for x86 (because running on a dozen Android things is easier than running a standard benchmark on Linux/Windows ofc). You find the results here: https://images.anandtech.com/doci/14892/spec2006-global-over... - I guess (not sure, because it's for some reason not cleary marked and mentioned...) these are SPECint2006-results. So, let's check them for validity (because WSL is no problem and it matches Linux ofc); just looking at an i7-6700K (which is a little bit behind the i9-9900K they supposedly ran on): https://www.spec.org/cpu2006/results/res2016q1/cpu2006-20160... - marginal worse performance than @anandtech in some benchmarks, but that's with an older CPU and an older arch! And then there are the 3 or 4 benchmarks which are just way off. Makes one wonder, what they really did (because of course, installing CentOS and running SPEC on native Linux is too much of a hassle, when running and compiling on 8 ARM-platforms!?)
EDITEDIT: it's even worse for SPECfp2006: https://www.spec.org/cpu2006/results/res2016q1/cpu2006-20160... [well, here the old 6700K suddenly sometimes is twice as fast as the 9900K and 3x as fast as the A13 (and yeah the story of the 2.8GHz-low-power-chip drawing circles around a 4.5GHz-HF-part just didn't sound convincing in the first place...)]