6 ms·

He has the history correct. Most of the CPUs that x86 beat in the market had superior FP performance; SPARCs, Alphas, PA-RISC, Itanium, etc. > When's the las

He has the history correct. Most of the CPUs that x86 beat in the market had superior FP performance; SPARCs, Alphas, PA-RISC, Itanium, etc. > When's the last time he actually did anything with a computer? According to Linus he completes about 30 pull requests a day. Some multiple of that in kernel builds. His $1900 32 core Threadripper speeds that process a great deal and FP contributes little to nothing. Today people stream video+audio, encrypt+decrypt and render graphics. All of these have specialized silicon. If their AVX-512 vanished in the night almost no one would notice the next day. Maybe we should all be astronomers and thermodynamicists writing bespoke finite element simulations and have a deep appreciation for the wonders of floating point ISAs, but that's just not the real world.

azalemeth 6y ago
Speaking as someone who does scientific computing all day long, in part with FEM simulations, even for me AVX512 isn't usually worth it in terms of wall-clock time.
- CamperBob2 6y ago
  Yes, it's pretty much useless, and Linus's reasoning will guarantee that things stay that way.
- sgillen 6y ago
  Speaking as someone else who does scientific computing all day, taking away vectorized operations would kill my performance completely.
TinkersW 6y ago
They wouldn't notice AVX512 vanishing because they never had it in the first place, as Intel hasn't shipped it in CPU people actually use for those tasks--just servers and random laptops. As for the rest, you are wrong, AVX/512 is not just floating point by any means, and floating point is used by more than just scientific workloads. Games/simulations/modeling software etc all can make heavy use of floating point.
CamperBob2 6y ago
He has the history correct. Most of the CPUs that x86 beat in the market had superior FP performance; SPARCs, Alphas, PA-RISC, Itanium, etc. This isn't a discussion about history, it's a discussion about SIMD FP instruction sets. Maybe we should all be astronomers and thermodynamicists writing bespoke finite element simulations and have a deep appreciation for the wonders of floating point ISAs, but that's just not the real world. Bullshit. Pure, unrefined organic bullshit. I can't begin to imagine why you, or Linus, or anyone even remotely conversant with computers would think this way. This attitude isn't just stupid, it's dangerously stupid. Influential people listen to Linus, and in this case, they shouldn't. Ever play a modern computer or console game? You're soaking in floating-point math. Ever do anything with graphics at all, for that matter? Run Photoshop or GIMP? That's all floating-point math under the hood... any nontrivial image processing work would be nightmarish without it. People used to spend hundreds of dollars on math coprocessors just to run Photoshop and similar creativity apps in the days before modern CPUs became fast enough to (apparently) be taken for granted. Ever play an MP3 on your PC, never mind a video? Do you think that any mainstream software implementations of those algorithms have been coded in fixed-point math at any time over the last twenty years? Never mind ML applications, which often use low-precision floats to maximize both dynamic range and memory efficiency. If there's a single trend that defines modern computing, it's the drive to turn everything into one big linear algebra problem and throw parallel FP execution units at it. It's grossly ignorant to say that floating point performance only matters to astronomers or physicists or engineers, and it's a genuine revelation to me -- and a disturbing one -- to realize that people still think this way. No, this isn't an apology for the debacle that is AVX-512, but... get real, no pun intended. It's not 1992 anymore.
- panpanna 6y ago
  This discussion is about avx512, which has shown to have some issues compared to other solutions. Nobody is claiming FP is garbage or that we don't ever need SIMD. Regarding Linus: he is almost always right. He has had more hands-on experience than everyone in this thread combined. I trust his judgement, he has earned it by being consistently correct while his opposition has just complained and eventually failed to deliver themselves.

azalemeth 6y ago

Speaking as someone who does scientific computing all day long, in part with FEM simulations, even for me AVX512 isn't usually worth it in terms of wall-clock time.

CamperBob2 6y ago
Yes, it's pretty much useless, and Linus's reasoning will guarantee that things stay that way.
sgillen 6y ago
Speaking as someone else who does scientific computing all day, taking away vectorized operations would kill my performance completely.

TinkersW 6y ago

They wouldn't notice AVX512 vanishing because they never had it in the first place, as Intel hasn't shipped it in CPU people actually use for those tasks--just servers and random laptops. As for the rest, you are wrong, AVX/512 is not just floating point by any means, and floating point is used by more than just scientific workloads. Games/simulations/modeling software etc all can make heavy use of floating point.

CamperBob2 6y ago

He has the history correct. Most of the CPUs that x86 beat in the market had superior FP performance; SPARCs, Alphas, PA-RISC, Itanium, etc. This isn't a discussion about history, it's a discussion about SIMD FP instruction sets. Maybe we should all be astronomers and thermodynamicists writing bespoke finite element simulations and have a deep appreciation for the wonders of floating point ISAs, but that's just not the real world. Bullshit. Pure, unrefined organic bullshit. I can't begin to imagine why you, or Linus, or anyone even remotely conversant with computers would think this way. This attitude isn't just stupid, it's dangerously stupid. Influential people listen to Linus, and in this case, they shouldn't. Ever play a modern computer or console game? You're soaking in floating-point math. Ever do anything with graphics at all, for that matter? Run Photoshop or GIMP? That's all floating-point math under the hood... any nontrivial image processing work would be nightmarish without it. People used to spend hundreds of dollars on math coprocessors just to run Photoshop and similar creativity apps in the days before modern CPUs became fast enough to (apparently) be taken for granted. Ever play an MP3 on your PC, never mind a video? Do you think that any mainstream software implementations of those algorithms have been coded in fixed-point math at any time over the last twenty years? Never mind ML applications, which often use low-precision floats to maximize both dynamic range and memory efficiency. If there's a single trend that defines modern computing, it's the drive to turn everything into one big linear algebra problem and throw parallel FP execution units at it. It's grossly ignorant to say that floating point performance only matters to astronomers or physicists or engineers, and it's a genuine revelation to me -- and a disturbing one -- to realize that people still think this way. No, this isn't an apology for the debacle that is AVX-512, but... get real, no pun intended. It's not 1992 anymore.

panpanna 6y ago
This discussion is about avx512, which has shown to have some issues compared to other solutions. Nobody is claiming FP is garbage or that we don't ever need SIMD. Regarding Linus: he is almost always right. He has had more hands-on experience than everyone in this thread combined. I trust his judgement, he has earned it by being consistently correct while his opposition has just complained and eventually failed to deliver themselves.