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RobotLocomotion / drake

Model-based design and verification for robotics.
https://drake.mit.edu
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Write unit tests that ensure multibody code does not do any dynamic memory allocation #10641

Closed amcastro-tri closed 8 months ago

amcastro-tri commented 5 years ago

We want to ensure that many of our building blocks in the multibody engine do not do any dynamic memory allocation after a context is created, for performance reasons.
For now this issue tracks:

  1. Inverse dynamics doesn't do any dynamic memory allocation. Unit tested.
  2. Mass matrix doesn't do any dynamic memory allocation. Unit tested.

from f2f @jwnimmer-tri, you mentioned you have ideas and even sample code for this?

amcastro-tri commented 5 years ago

FYI, for inverse dynamics only 5% of the cost goes to malloc/free calls, so not a real bottleneck but definitely nice fixing.

jwnimmer-tri commented 5 years ago

@amcastro-tri please try out #10650 and see if it's useful for this purpose.

jwnimmer-tri commented 5 years ago

FYI, for inverse dynamics only 5% of the cost goes to malloc/free calls, so not a real bottleneck ...

The usual complaint with mallocs is less that they degrade the mean throughput, but rather that they can introduce relatively high jitter for operations' latency, especially as system load increases. Code in Drake that is going to be used for real-time control should (ideally) be written to avoid allocations after some start-up phase.

sherm1 commented 4 years ago

Related: #13186