"calm function" inside source code

[Christian Jakob]

Hi,

I need a "calm function" for my generation process. In python code it looks like this:

def calm():
 for b in O.bodies:
  if isinstance(b.shape,Sphere) or b.isClump:
   b.state.vel = Vector3(0,0,0)
   b.state.angVel = Vector3(0,0,0)
   b.state.angMom = Vector3(0,0,0)

I detected, that it is very slow in the case it is called by PyRunner for e.g. every 2 steps.

O.engines=O.engines+[PyRunner(iterPeriod=2,command='calm()')]

Would it be faster, when it is implemented inside C++ source code?
If yes, where can I implement it (which file)?

Regards,

Christian

[Anton Gladky (gladky-anton)]

Hi,

pkg/dem/Shop.cpp should probably be the right place.
As an example, you can have a look, how "Shop::getSpheresMass" [1] and [2]
was implemented, it can be also useful to keep "mask" parameter for more
flexibility.

Do not forget to add a python-wrapper for this function into
py/_utils.cpp [3] and [4].

Have a luck!

Anton

[1] https://github.com/yade/trunk/blob/master/pkg/dem/Shop.hpp#L59
[2] https://github.com/yade/trunk/blob/master/pkg/dem/Shop.cpp#L295
[3] https://github.com/yade/trunk/blob/master/py/_utils.cpp#L404
[4] https://github.com/yade/trunk/blob/master/py/_utils.cpp#L456

[Jan Stránský (honzik)]

Hello Christian,

I would say it will be faster in c++ (as almost anything :-). Esepcially
here you can save a lot of time by changing allocation of new Vector3r
object for each particle to just rewriting doubles.

As the place I would use Shop.*pp file for c++ code and utils module for
python interface (if nobody else disagree).

regards
Jan

2012/7/18 Christian Jakob <email address hidden>

> Public bug reported:
>
> Hi,
>
> I need a "calm function" for my generation process. In python code it
> looks like this:
>
> def calm():
> for b in O.bodies:
> if isinstance(b.shape,Sphere) or b.isClump:
> b.state.vel = Vector3(0,0,0)
> b.state.angVel = Vector3(0,0,0)
> b.state.angMom = Vector3(0,0,0)
>
> I detected, that it is very slow in the case it is called by PyRunner
> for e.g. every 2 steps.
>
> O.engines=O.engines+[PyRunner(iterPeriod=2,command='calm()')]
>
> Would it be faster, when it is implemented inside C++ source code?
> If yes, where can I implement it (which file)?
>
> Regards,
>
> Christian
>
> ** Affects: yade
> Importance: Wishlist
> Status: New
>
> --
> You received this bug notification because you are a member of Yade
> developers, which is the registrant for Yade.
> https://bugs.launchpad.net/bugs/1026073
>
> Title:
> "calm function" inside source code
>
> Status in Yet Another Dynamic Engine:
> New
>
> Bug description:
> Hi,
>
> I need a "calm function" for my generation process. In python code it
> looks like this:
>
> def calm():
> for b in O.bodies:
> if isinstance(b.shape,Sphere) or b.isClump:
> b.state.vel = Vector3(0,0,0)
> b.state.angVel = Vector3(0,0,0)
> b.state.angMom = Vector3(0,0,0)
>
> I detected, that it is very slow in the case it is called by PyRunner
> for e.g. every 2 steps.
>
> O.engines=O.engines+[PyRunner(iterPeriod=2,command='calm()')]
>
> Would it be faster, when it is implemented inside C++ source code?
> If yes, where can I implement it (which file)?
>
> Regards,
>
> Christian
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/yade/+bug/1026073/+subscriptions
>
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[Christian Jakob (jakob-ifgt)]

Thank you for your help.

I think I did it, but there is a compilation warning:

/home/me/YADE/trunk/pkg/dem/Shop.cpp: In static member function ‘static Real Shop::calm(const boost::shared_ptr<Scene>&, int)’:
/home/me/YADE/trunk/pkg/dem/Shop.cpp:838: warning: no return statement in function returning non-void

Shall I say "return 0;" at the end of the function?

[Anton Gladky (gladky-anton)]

2012/7/18 Christian Jakob <email address hidden>:
> I think I did it, but there is a compilation warning:
>
> /home/me/YADE/trunk/pkg/dem/Shop.cpp: In static member function ‘static Real Shop::calm(const boost::shared_ptr<Scene>&, int)’:
> /home/me/YADE/trunk/pkg/dem/Shop.cpp:838: warning: no return statement in function returning non-void
>
> Shall I say "return 0;" at the end of the function?

Why not to declare it as "void", if you are not going to return any value?

Anton

[Jan Stránský (honzik)]

>
> Shall I say "return 0;" at the end of the function?
>

It is one option, or just change

static Real Shop::calm(const boost::shared_ptr<Scene>&, int)

to

static void Shop::calm(const boost::shared_ptr<Scene>&, int)

Jan

[Christian Jakob (jakob-ifgt)]

Jan and Anton, are you twins?

... you are giving same answer at the same time ^^

[Anton Gladky (gladky-anton)]

Something is wrong with Launchpad. It resends mails too late.

Anton

[Christian Jakob (jakob-ifgt)]

calm function is not working yet (see attachment)
it seems it does not set velocities to zero, I can see no effect at all ... ?!

[Jan Stránský (honzik)]

Hello Christian,

in PyRunner, instead of command='calm', try:

command='calm()'

with braces.

Jan

[Christian Jakob (jakob-ifgt)]

Ah, ok. Works fine with braces ;)