[bugfix]: honor collector masks in loss reductions - #4057
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PR pytorch#3888 routed objectives through _reduce_loss, but the helper still ignored ("collector", "mask") because the corresponding change in pytorch#3850 never merged. This fix excludes padded timesteps from loss reduction so they do not affect the loss or gradients.
🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/rl/4057
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August 2, 2026 01:23
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Aug 2, 2026
Unify unreduced mask behavior. Apply collector masks to REDQ under reduction="none". Remove unreachable mask-shape handling.
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#3888 refactored objectives to route through _reduce_loss but the collector mask change from #3850 never merged, leaving a gap. The relevant code changed as well. This made it so padded timesteps from collector, mask were still included and could change the final loss and grads.
BC & RND use it directly. A2C, ppo and reinforce pass input via TensorDict and REDQ/OnlineDT deal with shape-specific cases their own way.
closes #3866.
Ran tests; 9314 passed.
cc @vmoens