Original post is here: eklausmeier.goip.de
For comparing different machines I invert the Hilbert matrix
$$
H = \left(\begin{array}{ccccc} 1 & {1\over2} & {1\over3} & \cdots & {1\over n} \
{1\over2} & {1\over3} & {1\over4} & \cdots & {1\over n+1} \
{1\over3} & {1\over4} & {1\over5} & \cdots & {1\over n+2} \
\vdots & \vdots & \vdots & \ddots & \vdots \
{1\over n} & {1\over n+1} & {1\over n+2} & \cdots & {1\over2n-1}
\end{array} \right)
= \left( {\displaystyle {1\over i+j-1} } \right)_{ij}
$$
This matrix is known to have very high condition numbers. Program xlu5.c stores four double precision matrices of dimension $n$. Matrix H and A store the Hilbert matrix, X is the identity matrix, Y is the inverse of H. Finally the maximum norm of $I-H\cdot H^{-1}$ is printed, which should be zero. These four double precision matrices occupy roughly 1.6 MB for $n=230$.
1. Runtime on Ryzen, AMD Ryzen 5 PRO 3400G with Radeon Vega Graphics, max 3.7 GHz, as given by lscpu.
1$ time xlu5o3b 230 > /dev/null
2 real 0.79s
3 user 0.79s
4 sys 0
5 swapped 0
6 total space 0
Cache sizes within CPU are:
1L1d cache: 128 KiB
2L1i cache: 256 KiB
3L2 cache: 2 MiB
4L3 cache: 4 MiB
Required storage for above program is 4 matrices, each having 230x230 entries with double (8 bytes), giving 1692800 bytes, roughly 1.6 MB.
2. Runtime on AMD FX-8120, Bulldozer, max 3.1 GHz, as given by lscpu.
1$ time xlu5o3b 230 >/dev/null
2 real 1.75s
3 user 1.74s
4 sys 0
5 swapped 0
6 total space 0
Cache sizes within CPU are:
1L1d cache: 64 KiB
2L1i cache: 256 KiB
3L2 cache: 8 MiB
4L3 cache: 8 MiB
3. Runtime on Intel, Intel(R) Core(TM) i5-4250U CPU @ 1.30GHz, max 2.6 GHz, as given by lscpu.
1$ time xlu5o3b 230 > /dev/null
2 real 1.68s
3 user 1.67s
4 sys 0
5 swapped 0
6 total space 0
Cache sizes within CPU are:
1L1d cache: 64 KiB
2L1i cache: 64 KiB
3L2 cache: 512 KiB
4L3 cache: 3 MiB
Apparently the Ryzen processor can outperform the Intel processor on cache, higher clock frequency. But even for smaller matrix sizes, e.g., 120, the Ryzen is two times faster.
Interestingly, the error in computations are different!
AMD and Intel machines run Arch Linux with kernel version 5.9.13, gcc was 10.2.0.
4. Runtime on Raspberry Pi 4, ARM Cortex-A72, max 1.5 GHz, as given by lscpu.
1$ time xlu5 230 > /dev/null
2 real 4.37s
3 user 4.36s
4 sys 0
5 swapped 0
6 total space 0
Linux 5.4.83 and GCC 10.2.0.
5. Runtime on Odroid XU4, Cortex-A7, max 2 GHz, as given by lscpu.
1$ time xlu5 230 > /dev/null
2 real 17.75s
3 user 17.60s
4 sys 0
5 swapped 0
6 total space 0
So the Raspberry Pi 4 is clearly way faster than the Odroid XU4.
