Re:Memory access on the Apple M1 processor
by titzer on Wednesday January 06, 2021 @05:32PM
(#25663576)
Frankly, I find Lemire does oversimplified, poor-quality control, back-of-the-envelope microbenchmarking all the time that provides little to no insight other than establishing a general trend. It's sophomoric and a poor demonstration about how to well-controlled benchmarking that might yield useful, repeatable, and transferrable results.
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Re:Memory access on the Apple M1 processor
by alecco on Wednesday January 06, 2021 @06:25PM
(#25664202)
Can you give an example? I've seen Lemire correct his posts on many occasions and the source code is published. I don't know many blogs doing anything remotely like that.
Re:Memory access on the Apple M1 processor
by titzer on Wednesday January 06, 2021 @06:34PM
(#25664313)
Sure. He often benchmark some small C++ code on his "laptop" CPU (which one exactly? microarchs matter!) and then committing classic microbenchmarking pitfalls such as:
- benchmarking something small enough to inspect machine code, but not inspecting machine code
- not plotting distribution, average, variance etc
- no attention paid to CPU frequency governor settings
- measuring too short a run
- measuring too small a dataset that it fits entirely in L1