Batches with threads introduce roundoff error, which can effect adaptive timestep

PetaVision / OpenPV

PetaVision is a C++ library for designing and deploying large-scale neurally-inspired computational models.

http://petavision.github.io

Eclipse Public License 1.0

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Batches with threads introduce roundoff error, which can effect adaptive timestep #9

Open slundqui opened 9 years ago

slundqui commented 9 years ago

Various testing with batches shows that there exists a 1e-3 error in timeScaleTrue between a run with no batches versus a run greater than 8 batches running on the same images. As the timeScaleTrue converges, this roundoff error can trigger the timeScale reset (due to timeScaleTrue decreasing), making the 2 runs that should be identical diverge. Keep this in mind when running with batches, as you may need to change your dtChangeMin accordingly.

Sheng

dpaiton commented 9 years ago

Marked as a bug. Although maybe just posting a warning to the user is a sufficient fix for now.

slundqui commented 9 years ago

Marked as wontfix, as roundoff errors is not a bug, but a property of being parallel.