# yade-users team mailing list archive

## Re: [Question #676451]: optimize camputational time for vibrated granular media

Bruno Chareyre proposed the following answer:
It is difficult for me to understand the meaning of various values of
Could you give raw times?

I understand that something is transient physically but it doesn't seem to mater really in terms of speed. Why do you think so?
For instance 2000 spheres give (3rd column is speed):

20000 0.269857831466 3415.36292082 3.239 0.00195161180227
30000 0.404786747199 1349.67539933 9.901 0.00198843695584
40000 0.539715662932 1214.09029787 17.085 0.00106745354645
50000 0.674644578665 1199.2390826 24.621 0.00122919908665
...
190000 2.56364939893 1258.1333534 131.847 0.00197268858104
200000 2.69857831467 1269.76190104 139.55 0.00190037774033
210000 2.8335072304 1351.34040383 147.32 0.00169256567465
...
440000 5.93687229221 1357.22627666 326.907 0.000706448896021
450000 6.07180120794 1374.03537234 334.778 0.000549054156559
460000 6.20673012367 1322.66851309 342.658 0.000677048337406

The transient aspect of it is not obvious... I don't think it explains
our different conclusions.

For 200 spheres:

10000 0.134928915733 85606.0606061 0.457 0.0
20000 0.269857831466 18590.9408551 0.9 0.00123066523288
30000 0.404786747199 16420.3612479 1.486 0.000652081911623
...
190000 2.56364939893 14819.7952972 11.095 0.00067976598448
200000 2.69857831467 16289.4412128 11.704 0.000573059522713
210000 2.8335072304 16424.248529 12.302 0.000804168697981

Still no clear trend after 20k.
The ratio of final speed is ~11 for a ratio in numbers of 10. Still close to linear.
Unless you have a sudden decrease of speed after 800k iterations I can't reproduce or explain your results.
How many cores do you have in total?
Did you try verlet=0.5*r for 2k spheres? You timings suggest that the cost of virtual interactions is excessively large and could be reduced by running the collider a bit more.

Bruno

--