unsloth/studio/backend/tests/test_training_nan_loss_handling.py
Daniel Han 3733e0b274
fix(studio): surface live step with null loss through the SSE progress stream (#6206)
* fix(studio): surface live step with null loss through the SSE progress stream

The metric histories skip non-finite steps, so during a NaN stretch the
SSE live loop and final complete event replayed the last finite
step/loss pair. Follow the live progress step when it is ahead of the
history tail and report its loss honestly (null until recovery).

Completes the NaN honesty fix for the SSE consumer flagged in review.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Apply live-step handling to inactive streams and clear the UI loss on null for PR #6206

Fresh /progress connections after a finished run took the inactive branch
which still replayed the last finite step and loss pair; apply the same
live-step correction there. On the frontend, applyProgress kept the stale
currentLoss when a payload advanced the step with a null loss; clear it so
the display shows -- until the loss recovers. Widen the runtime state type
to number | null, which the view layer already handles.

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
2026-06-11 07:50:13 -07:00

110 lines
4.2 KiB
Python

# SPDX-License-Identifier: AGPL-3.0-only
# Copyright 2026-present the Unsloth AI Inc. team. All rights reserved.
"""Pin Studio's behavior when a training event reports non-finite (NaN/Inf) loss.
The training event handler used to filter NaN/Inf to None silently while
leaving the previous finite loss in progress.loss — so the API kept reporting
the stale value as if everything were fine. We now drop the stale value:
clients see loss=None at the affected step and a one-shot warning is logged.
Training continues; the run is not marked failed.
"""
from __future__ import annotations
import math
import os
import sys
import pytest
_BACKEND = os.path.join(os.path.dirname(__file__), "..")
if _BACKEND not in sys.path:
sys.path.insert(0, _BACKEND)
from core.training.training import TrainingBackend
def _make_backend() -> TrainingBackend:
return TrainingBackend()
def _progress_event(
step: int,
loss: float,
lr: float = 1e-4,
) -> dict:
return {
"type": "progress",
"step": step,
"loss": loss,
"learning_rate": lr,
"epoch": 0.0,
"total_steps": 100,
}
class TestNonfiniteLossSoftHandling:
def test_finite_loss_updates_progress_normally(self):
b = _make_backend()
b._handle_event(_progress_event(step = 1, loss = 0.97))
assert b._progress.loss == pytest.approx(0.97)
assert b._progress.error is None
assert b._should_stop is False
assert getattr(b._progress, "_nonfinite_loss_warned", False) is False
def test_nan_loss_clears_progress_loss(self):
b = _make_backend()
b._handle_event(_progress_event(step = 1, loss = 0.97))
assert b._progress.loss == pytest.approx(0.97)
b._handle_event(_progress_event(step = 2, loss = float("nan")))
# Stale finite loss must NOT leak through
assert b._progress.loss is None
# Run is not marked failed
assert b._progress.error is None
assert b._should_stop is False
# Warning flag is set so we don't re-log on every subsequent NaN step
assert b._progress._nonfinite_loss_warned is True
def test_inf_loss_clears_progress_loss(self):
b = _make_backend()
b._handle_event(_progress_event(step = 1, loss = float("inf")))
assert b._progress.loss is None
assert b._progress.error is None
assert b._should_stop is False
assert b._progress._nonfinite_loss_warned is True
def test_negative_inf_loss_clears_progress_loss(self):
b = _make_backend()
b._handle_event(_progress_event(step = 1, loss = float("-inf")))
assert b._progress.loss is None
assert b._progress.error is None
assert b._should_stop is False
assert b._progress._nonfinite_loss_warned is True
def test_repeated_nan_only_warns_once(self):
"""Subsequent NaN events must not re-fire the warning flag setter.
The flag should already be True after the first NaN."""
b = _make_backend()
b._handle_event(_progress_event(step = 1, loss = 0.97))
b._handle_event(_progress_event(step = 2, loss = float("nan")))
assert b._progress._nonfinite_loss_warned is True
# Further NaN steps don't change anything we care about
b._handle_event(_progress_event(step = 3, loss = float("nan")))
b._handle_event(_progress_event(step = 4, loss = float("nan")))
assert b._progress._nonfinite_loss_warned is True
assert b._progress.loss is None
assert b._progress.error is None
assert b._should_stop is False
def test_recovery_updates_loss_when_finite_again(self):
"""If a NaN step is followed by a finite step, progress.loss must
reflect the new finite value (not stay stuck at None)."""
b = _make_backend()
b._handle_event(_progress_event(step = 1, loss = 0.97))
b._handle_event(_progress_event(step = 2, loss = float("nan")))
assert b._progress.loss is None
b._handle_event(_progress_event(step = 3, loss = 0.85))
assert b._progress.loss == pytest.approx(0.85)
# Warning flag stays set (we don't reset it on recovery)
assert b._progress._nonfinite_loss_warned is True