fix the grad_acc issue at epoch boundaries (#24415)
* fix the grad_acc issue at epoch boundaries
Co-Authored-By: Zach Mueller <7831895+muellerzr@users.noreply.github.com>
* add contributors.
Co-authored-by: sumpster
* address comments
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Co-authored-by: Zach Mueller <7831895+muellerzr@users.noreply.github.com>
