Hi, On Mon, Dec 05 2022, AW wrote:
Am Montag, 5. Dezember 2022, 09:21:03 CET schrieb Martin Jambor:
The fact is that -v3 baseline means better floating point performance out of the box. That is why many think it is the right choice for a new product that will be deployed almost exclusively on new hardware. No need to invent conspiracy theories to explain what is happening.
Thank you very much for this start of an explanation. You see, even here on this list people lack the technical knowledge about advantages of -v3 and thus it's a good move to explain it.
I have shared SPEC results illustrating the point on this mailing list in the summer (and they are still available at https://jamborm.github.io/spec-2022-07-29-levels/index.html )
May I ask you to amend your answer a bit to the part »out of the box«?
The software you install from Tumbleweed repositories target the distribution base ISA (Instruction Set Architecture) which is currently v1. If the base was moved to v3, those programs would use AVX256 which quite often speeds floating-point operations. See e.g. ImageMagick results in the report linked above.
Does this mean -- right now -- that all the machines running TW and with a -v3 capable CPU don't get the improved floating point performance at all OR that they get it nonetheless, because -- while it does not work out of the box -- TW somehow manages to use the -v3 advantages?
Often they don't. To get the performance advantage you'd have to build the programs yourself of install them from a source which compiles them targeting a more recent ISA. The exception is software where the authors themselves included specialized versions of heavily used functions which take advantage of new CPUs and run those if a new CPU is detected. Video codecs and glibc string functions fall into this category. I hope this explains it, Martin