yade-dev team mailing list archive

[Bruno Chareyre <1475844@xxxxxxxxxxxxxxxxxx>]

@Vaclav
>I removed this functor caching, since it does not seem to bring any benefit performance-wise.

IIRC the change [1] gave a significant (clearly measurable) speedup.
Before the change it was like this:

if (noIGfuntor || noIPfunctor) assignIGfunctor();
if (!IGfunctor.go()) continue;
assignIPfunctor();

For virtual interactions (large majority, typically) it was assigning IGfunctor again and again, at each iteration.
I don't know in which circumstances you made the comparison but it could be that the gain from caching was hidden by this small bug.
Ultimately, I guess queuing separately the interactions which have or do not have functor would be better, since it would remove a "if".
It reminds me a discussion with Colin Thornton when he said: "they invented vector processing, the BIG thing, then they realized that our programs contain "if" statements, F##@!!"
B

[1]
https://github.com/yade/trunk/commit/15182aca8473be86c74b139731dbb88b0007f759
#diff-726aef96982e392072499e825cf634b4L106

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https://bugs.launchpad.net/bugs/1475844

Title:
  Swap problem in InteractionLoop

Status in Yade:
  New

Bug description:
  When you use two different materials, it might happen that
  IntreactionLoop ends with error [1]. It is because of IPhys stage (see
  also the comment in [1], but in reality Ip2 can by non-symmetric).

  Possible solutions:
  1) define both Ip2_Mat1_Mat2 and Ip2_Mat2_Mat1 (according to [2] maybe does not work..)
  2) replace assert [1] (something like   if (swap) { I->functorCase.phys=physDispatcher->getFunctor2D(b2->material,b1->material,swap); swap=false }). Is the assert necessary at all?
  3) make option 1) somehow automatic (using some macro?)

  Pros and cons:
  1) would mess the source code and documentation a bit, but otherwise I think it is ok
  2) would it have some side effects? Is it ok for Law2 stage? etc etc?
  3) maybe the best option if the solution is reasonable

  cheers
  Jan

  [1] http://bazaar.launchpad.net/~yade-pkg/yade/git-trunk/view/head:/pkg/common/InteractionLoop.cpp#L116
  [2] https://answers.launchpad.net/yade/+question/269315

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