Compilation of FET under GNU/Linux

[Liviu Lalescu]

I have a 12 threads (6 cores) Ryzen 1600 CPU. I compile FET with "make -j 12".

Usually, FET compilation took 2 minutes 50 seconds. I had Linux kernel 4.4.114. Today my openSUSE upgraded to kernel 4.4.120 and the FET compilation takes 2 minutes 33 seconds only. So about 10% faster. Isn't this very interesting?!

Incredible: also running FET (single generation -- single core) is faster. Instead of 44 seconds I get 40 seconds on the same file with the same starting random seed

[Liviu Lalescu]

At boot time, it said a brief message: "Vulnerable to Spectre V2". So, as explained here: https://forums.opensuse.org/showthread.php/530316-Updating-to-kernel-4-4-120-45-1-leads-to-quot-System-may-be-vulnerable-to-spectre-v2-quot , I upgraded my nVidia drivers (I have nVidia GTX 1050).

Unfortunately, now the speed is the same as before: 2 m 49 s compilation on 12 threads and 44 seconds generation on a single thread.

I am really puzzled   How was the speedup possible?

[Volker Dirr]

hmmm... i don't think so, but you might install previous software/video and recheck.

i guess there might be an other effect: yesterday morning was a cold day in Romania? So you opened your window in the morning for air ventilation and so cold air was moving though your case. So the CPU was able to boost clock speed longer than with closed windows and higher temperature?

[Liviu Lalescu]

hmmm... i don't think so, but you might install previous software/video and recheck.

Seems no longer available: https://download.nvidia.com/opensuse/leap/42.3 , G04 - I had 384, now it is 390.

i guess there might be an other effect: yesterday morning was a cold day in Romania? So you opened your window in the morning for air ventilation and so cold air was moving though your case. So the CPU was able to boost clock speed longer than with closed windows and higher temperature?

No, it was clearly from the software   Since three months I got the computer and compilation time and generation single thread were similar, then immediately the speedup after kernel 4.4.120, then immediately speed down after installing nVidia updates.

[Volker Dirr]

hmm.. Maybe you can reproduce by removing nvidia and use only a default vga driver without official nvidida driver?

[Volker Dirr]

Maybe the G04 384 from 42.2 also work:
https://download.nvidia.com/opensuse/leap/42.2/x86_64/

[Liviu Lalescu]

hmm.. Maybe you can reproduce by removing nvidia and use only a default vga driver without official nvidida driver?

1. My screen resolution when installing openSUSE, before installing the nVidia drivers, is 640x480 (very difficult to work with).

2. I am afraid. I don't want to be forced to reinstall/reconfigure my GNU/Linux (which is not very difficult, but takes a few hours).

[Liviu Lalescu]

Maybe the G04 384 from 42.2 also work:
https://download.nvidia.com/opensuse/leap/42.2/x86_64/

I don't think so. But anyway it is risky, I might be forced to reinstall the system.

[Liviu Lalescu]

I did not want to let Volker down, and I also wanted to satisfy the natural curiosity.

I removed the nVidia drivers, went to the free software (open source) nouveau, in 640x480 resolution. Unfortunately, 43 seconds of generating on a single thread (usual time). I did not try to compile FET, I consider it is not necessary.

I then tried to install the nVidia 384 drivers for the old openSUSE Leap 42.2, as Volker suggested. The installer complained about ksym dependency missing. I let it complain and installed 384. But it booted with 640x480 resolution. So I did not run FET, considering it useless (I might have done it, though).

Now, fortunately, installing the corresponding nVidia drivers put things back to normal; I don't have to reinstall my system.

As a note, the boot messages did not show "vulnerable to spectre V2" or similar, in no variant above.

Now the times are also usual.

It will remain for now a mystery

[Liviu Lalescu]

I updated the BIOS, and reset the values to defaults. I have let the memory to a lower frequency (its default): 2400 MHz instead of 2933 MHz. Now FET solves this file in 40-41 seconds, and FET compiles in ~2m 39s (so, faster than the usual)

[Liviu Lalescu]

Just checked also on my Windows 10. I usually got ~55 seconds, now I got (testing once) 54 seconds. So it is only faster on GNU/Linux.

[Liviu Lalescu]

GNU/Linux, Qt 5.11.0, FET still solves the usual file with the usual starting random seed in 40 seconds (which is faster than I was used to).

GNU/Linux, very old Qt 4.8.7, FET solved the usual file with the usual starting random seed in 38 seconds.