Fix incorrect caching of MetricCollection (#2571)

* Fix incorrect caching of MetricCollection

Also update tests to correctly test for #2211.
Also add return deepcopy values of compute

* Update Changelog

* fix issues with deepcopy by using .clone

---------

Co-authored-by: Nicki Skafte Detlefsen <skaftenicki@gmail.com>
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
Co-authored-by: Jirka Borovec <6035284+Borda@users.noreply.github.com>
(cherry picked from commit 6a23b38)

CHANGELOG.md

@@ -26,6 +26,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Fixed bug in `MetricCollection` when using compute groups and `compute` is called more than once ([#2571](https://github.com/Lightning-AI/torchmetrics/pull/2571))
+
+
 - Fixed class order of `panoptic_quality(..., return_per_class=True)` output ([#2548](https://github.com/Lightning-AI/torchmetrics/pull/2548))
 
 

src/torchmetrics/collections.py

@@ -187,6 +187,11 @@ def __init__(
 
         self.add_metrics(metrics, *additional_metrics)
 
+    @property
+    def metric_state(self) -> Dict[str, Dict[str, Any]]:
+        """Get the current state of the metric."""
+        return {k: m.metric_state for k, m in self.items(keep_base=False, copy_state=False)}
+
     @torch.jit.unused
     def forward(self, *args: Any, **kwargs: Any) -> Dict[str, Any]:
         """Call forward for each metric sequentially.
@@ -206,6 +211,11 @@ def update(self, *args: Any, **kwargs: Any) -> None:
         """
         # Use compute groups if already initialized and checked
         if self._groups_checked:
+            # Delete the cache of all metrics to invalidate the cache and therefore recent compute calls, forcing new
+            # compute calls to recompute
+            for k in self.keys(keep_base=True):
+                mi = getattr(self, str(k))
+                mi._computed = None
             for cg in self._groups.values():
                 # only update the first member
                 m0 = getattr(self, cg[0])
@@ -304,7 +314,6 @@ def _compute_groups_create_state_ref(self, copy: bool = False) -> None:
                         # Determine if we just should set a reference or a full copy
                         setattr(mi, state, deepcopy(m0_state) if copy else m0_state)
                     mi._update_count = deepcopy(m0._update_count) if copy else m0._update_count
-                    mi._computed = deepcopy(m0._computed) if copy else m0._computed
         self._state_is_copy = copy
 
     def compute(self) -> Dict[str, Any]:

src/torchmetrics/metric.py

@@ -630,6 +630,8 @@ def wrapped_func(*args: Any, **kwargs: Any) -> Any:
                 should_unsync=self._should_unsync,
             ):
                 value = _squeeze_if_scalar(compute(*args, **kwargs))
+                # clone tensor to avoid in-place operations after compute, altering already computed results
+                value = apply_to_collection(value, Tensor, lambda x: x.clone())
 
             if self.compute_with_cache:
                 self._computed = value

tests/unittests/bases/test_collections.py

@@ -452,10 +452,29 @@ def test_check_compute_groups_correctness(self, metrics, expected, preds, target
             for key in res_cg:
                 assert torch.allclose(res_cg[key], res_without_cg[key])
 
+            # Check if second compute is the same
+            res_cg2 = m.compute()
+            for key in res_cg2:
+                assert torch.allclose(res_cg[key], res_cg2[key])
+
             if with_reset:
                 m.reset()
                 m2.reset()
 
+        # Test if a second compute without a reset is the same
+        m.reset()
+        m.update(preds, target)
+        res_cg = m.compute()
+        # Simulate different preds by simply inversing them
+        m.update(1 - preds, target)
+        res_cg2 = m.compute()
+        # Now check if the results from the first compute are different from the second
+        for key in res_cg:
+            # A different shape is okay, therefore skip (this happens for multidim_average="samplewise")
+            if res_cg[key].shape != res_cg2[key].shape:
+                continue
+            assert not torch.all(res_cg[key] == res_cg2[key])
+
     @pytest.mark.parametrize("method", ["items", "values", "keys"])
     def test_check_compute_groups_items_and_values(self, metrics, expected, preds, target, method):
         """Check states are copied instead of passed by ref when a single metric in the collection is access."""