Yeb Havinga wrote:
model name      : AMD Phenom(tm) II X4 940 Processor @ 3.00GHz
cpu cores         : 4
stream compiled with -O3
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:       5395.1815       0.0089       0.0089       0.0089

For comparison sake, an only moderately expensive desktop Intel CPU using DDR3-1600:

model name    : Intel(R) Core(TM) i7 CPU         860  @ 2.80GHz
cpu cores    : 4
siblings    : 8
Number of Threads requested = 4
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:      13666.0986       0.0108       0.0107       0.0108

8 hyper-threaded cores here. They work well for improving CPU-heavy tasks, but with 4 threads total is where the memory throughput maxes out at.

I'm not sure if Yeb's stream was compiled to use MPI correctly though, because I'm not seeing "Number of Threads" in his results. Here's what works for me:

 gcc -O3 -fopenmp stream.c -o stream

And then you can set:

export OMP_NUM_THREADS=4

Or whatever you want in order to control the number of threads it uses inside. Here's the way scaling works on my processor:

Number of Threads requested = 1
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:       9806.2648       0.0150       0.0149       0.0151

Number of Threads requested = 2
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:      12495.2113       0.0117       0.0117       0.0118

Number of Threads requested = 3
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:      13388.7187       0.0111       0.0109       0.0126

Number of Threads requested = 4
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:      13695.6611       0.0107       0.0107       0.0108

Number of Threads requested = 5
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:      12651.7200       0.0116       0.0116       0.0116

Number of Threads requested = 6
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:      12804.7192       0.0115       0.0114       0.0117

Number of Threads requested = 7
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:      12670.2525       0.0116       0.0116       0.0117

Number of Threads requested = 8
Function      Rate (MB/s)   Avg time     Min time     Max time
Triad:      12468.5739       0.0119       0.0117       0.0131

--
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
g...@2ndquadrant.com   www.2ndQuadrant.us


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