Unverified Commit 45a6fa6d authored by moebiusband73's avatar moebiusband73 Committed by GitHub
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Update README.md

parent dce72b45
......@@ -88,9 +88,9 @@ To run the benchmark call:
The benchmark will output the results similar to the stream benchmark. Results are validated.
For threaded execution it is recommended to control thread affinity.
We recommend to use likwid-pin for benchmarking:
We recommend to use likwid-pin for setting the number of threads used and to control thread affinity:
likwid-pin -c 0-3 ./bwbench-GCC
likwid-pin -C 0-3 ./bwbench-GCC
Example output for threaded execution:
......@@ -118,3 +118,42 @@ SDaxpy: 46822.63 23411.32 0.0281 0.0273 0.0325
Solution Validates
## Scaling runs
Apart from the highest sustained memory bandwidth often also the scaling behavior within memory domains is a important system property.
There is a helper script included in util (```extractResults.pl```) that creates a text result file from multiple runs that can be used as input to plotting applications as gnuplot and xmgrace.
This involves two steps: Executing the benchmark runs and then creating the data file.
To run the benchmark for different thread counts within a memory domain execute (this assumes bash or zsh):
$ for nt in 1 2 4 6 8 10; do likwid-pin -q -C E:M0:$nt:1:2 ./bwbench-ICC > dat/emmy-$nt.txt; done
It is recommended to just use one thread per core in case the processor support hyperthreading.
Use whatever stepping you like, here a stepping of two was used.
The ```-q``` option suppresses output from ```likwid-pin```.
Above line uses the expression based syntax, on systems with hyperthreading enabled (check with, e.g., ```likwid-topology```) you have to skip the other hardware threads on each core.
For above system with 2 hardware threads per core this results in ```-C E:M0:$nt:1:2```, on a system with 4 hardware threads per core you would need ```-C E:M0:$nt:1:4```.
The string before the dash (here emmy) can be arbitrary, but the after the dash the extraction script expects the thread count.
Also the file ending has to be ```.txt```.
Please check with a text editor on some result files if everything worked fine.
To extract the results and output in a plotable format execute:
./extractResults.pl ./dat
The script will pick up all result files in the directory specified and create a column format output file.
In this case:
#nt Init Sum Copy Update Triad Daxpy STriad SDaxpy
1 4109 11900 5637 8025 7407 9874 8981 11288
2 8057 22696 11011 15174 14821 18786 17599 21475
4 15602 39327 21020 28197 27287 33633 31939 37146
6 22592 45877 29618 37155 36664 40259 39911 41546
8 28641 46878 35763 40111 40106 41293 41022 41950
10 33151 46741 38187 40269 39960 40922 40567 41606
Please be aware the the single core memory bandwidth as well as the scaling behavior depends on the frequency settings.
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