andrea onofri
MModular
•Created by andrea onofri on 1/26/2025 in #questions
Parallelize in Mandelbrot example do not use all physical cores of an Intel Core i9 CPU
In my experience using all physical core is profitable also considering a tail for slower threads.
But you surely know better than me what is better for Mojo in this stage of teething.
Thanks again for the kind reply.
8 replies
MModular
•Created by andrea onofri on 1/26/2025 in #questions
Parallelize in Mandelbrot example do not use all physical cores of an Intel Core i9 CPU
I understand (and agree) that GPU is now the main priority.
So I propose only a default change, that should be very easy to implement.
I propose to change parallelize default from num_performance_cores() to num_physical_cores().
Leaving the current default, on many CPU only a fraction of available computation power is actually used.
For example on my CPU only 8 physical core are used, but 24 are available.
Is not exactly 8/24 = 1/3 because the 16 not performance cores can be slower (but the main difference is they do not support hyperthreading).
Using less than half of the available cores is not a good presentation card, especially for newcomers to a language devoted to the full use of unused resources as vectorial ops multicore and GPUs.
I think that changing this default would be beneficial also for tasks less embarrassing parallel than Mandelbrot set, e.g. matmul.
Probably you haven't spotted this problem because on higher level CPU all physical cores are performance cores.
As is the case for the CPU (Xeon Platinum 8481C) used for Mandelbrot in "How Mojo🔥 gets a 35,000x speedup over Python" https://www.modular.com/blog/how-mojo-gets-a-35-000x-speedup-over-python-part-1.
(Sorry for the multiple messages, I am new also to discord and I don't know how to add newlines.)
8 replies
MModular
•Created by andrea onofri on 1/26/2025 in #questions
Parallelize in Mandelbrot example do not use all physical cores of an Intel Core i9 CPU
But I still think that physical cores would be a better default. I agree that logical core is not a good default, because this would use hyperthreading by default.
8 replies
MModular
•Created by andrea onofri on 1/26/2025 in #questions
Parallelize in Mandelbrot example do not use all physical cores of an Intel Core i9 CPU
Thanks for the reply!
8 replies