Re: 1-wire behaviour on Bookworm

On 20/09/2024 00:50, Lawrence D'Oliveiro wrote:

On Thu, 19 Sep 2024 10:36:16 +0100, druck wrote:

With the Pi 3B, I could either read the sensors sequentially taking
about 0.9s each, or using threads simultaneously in 1.0s. The Pi 4B with
Bookworm reads the sensors sequentially a shade faster at just over
0.8s, but when reading simultaneously, returns 2 after 0.8s, another 2
after 1.6s and the last two at 2.4s.

Is this Python code? Python threading cannot currently take full advantage
of multiple CPUs, owing to having to serialize all interpreter operations
through the “Global Interpreter Lock”.

It's a C program using posix threads.

I did initially write a Python version using the ThreadPool from
multiprocessing.dummy It is only milliseconds slower than the C as the
Python threads are able to yield when goes out to the system to read the
files in /sys/bus/w1/devices/

This is going to be fixed from 3.13 onwards.

That will be very useful for pure Python code. They are making things a
bit challenging by deprecating some other things before getting there,
which I'll need to sort out before moving on from 3.11.

---druck