Not sure if anyone has posted results for this as requested, but here's a run on an RPi3B+, gcc 8.2.0, gentoo-on-rpi3-64bit image, with and without -ffast-math (as expected, on arm64 this flag makes essentially no difference), FLIRC case, on-demand governor:ejolson wrote: ↑Wed Dec 05, 2018 6:00 amIn a different thread appears a short self-contained C program which computes the first Fibonacci number with a million digits. This program implements big-number arithmetic using 64-bit integers as the underlying type. The Pi 3B+ running in 32-bit compatibility mode completes the computation in 15.43 seconds. Based on rescaling the clock speeds of a different ARM-based single-board computer, it was estimated that the Pi 3B+ running in 64-bit mode should complete this same computation in only 7.49 seconds. If true, that would be a two-fold increase in speed for a particular application just by switching operating systems.

It would be nice if someone who is running a 64-bit operating system on real 3B+ hardware could confirm that this estimate is correct. The program is available in this post. The above mentioned performance results are discussed in subsequent posts of the same thread.

Code: Select all

```
demouser@pi64 ~ $ gcc -O3 -ffast-math -o fibonacci fibonacci.c -lm
demouser@pi64 ~ $ time ./fibonacci | head -c 32
10727395641800477229364813596225
real 0m7.746s
user 0m7.713s
sys 0m0.032s
demouser@pi64 ~ $ time ./fibonacci | tail -c 32
4856539211500699706378405156269
real 0m7.818s
user 0m7.764s
sys 0m0.033s
demouser@pi64 ~ $ gcc -O3 -o fibonacci fibonacci.c -lm
demouser@pi64 ~ $ time ./fibonacci | head -c 32
10727395641800477229364813596225
real 0m7.740s
user 0m7.713s
sys 0m0.024s
demouser@pi64 ~ $ time ./fibonacci | tail -c 32
4856539211500699706378405156269
real 0m7.813s
user 0m7.795s
sys 0m0.017s
```