3 ms·
There’s nothing wrong with dropping the clock speed when the whole point of SIMD instructions is that they execute on multiple data. As long as the clock speed
by physicsguy 7y ago
There’s nothing wrong with dropping the clock speed when the whole point of SIMD instructions is that they execute on multiple data. As long as the clock speed drop beats the multiplicative speedup from doing 4x/8x/whatever operations in parallel, it’s fine
- stingraycharles 7y agoMy point is that the clock speed is also dropped for other processes. So it's not a simple heuristic "oh if we have more data than X we can use AVX512 instead of AVX256", because you do not know what other processes are doing, and they will be slowed down as well. This type of heuristic only works if you are the sole users of the server, e.g. a database server.
- vnorilo 7y agoThe problem is that the architecture in question would take forever in cpu time terms to switch back and forth, so a sprinkle of heavy avx512 was the worst of all worlds. In addition, some cpus would emulate 512 with half width micro-ops during voltage ramp up. Yes, it sounds crazy.
- temac 7y agoNot it is not fine at all. If you have too many instructions but not enough, your whole CPU will run slower mostly on non AVX-512 instructions, and maybe even your whole package => the end result will just be slower. Not to say that those processors are bad, but AVX-512 on them is for niche workloads.