FIX AffinityPropagation fix results with float32 input (#17995)

amy12xx · web-flow · commit 3cb3d4109e7a · 2020-07-26T15:22:30.000+02:00
diff --git a/doc/whats_new/v0.24.rst b/doc/whats_new/v0.24.rst
@@ -70,6 +70,10 @@ Changelog
   `init_size_`, are deprecated and will be removed in 0.26. :pr:`17864` by
   :user:`Jérémie du Boisberranger <jeremiedbb>`.
 
+- |Fix| Fixed a bug in :class:`cluster.AffinityPropagation`, that
+  gives incorrect clusters when the array dtype is float32.
+  :pr:`17995` by :user:`Thomaz Santana  <Wikilicious>` and :user:`Amanda Dsouza <amy12xx>`.
+
 :mod:`sklearn.covariance`
 .........................
 
diff --git a/sklearn/cluster/_affinity_propagation.py b/sklearn/cluster/_affinity_propagation.py
@@ -162,7 +162,7 @@ def affinity_propagation(S, *, preference=None, convergence_iter=15,
     tmp = np.zeros((n_samples, n_samples))
 
     # Remove degeneracies
-    S += ((np.finfo(np.double).eps * S + np.finfo(np.double).tiny * 100) *
+    S += ((np.finfo(S.dtype).eps * S + np.finfo(S.dtype).tiny * 100) *
           random_state.randn(n_samples, n_samples))
 
     # Execute parallel affinity propagation updates
diff --git a/sklearn/cluster/tests/test_affinity_propagation.py b/sklearn/cluster/tests/test_affinity_propagation.py
@@ -231,3 +231,16 @@ def test_affinity_propagation_convergence_warning_dense_sparse(centers):
         assert_array_equal(ap.predict(X),
                            np.zeros(X.shape[0], dtype=int))
     assert len(record) == 0
+
+
+def test_affinity_propagation_float32():
+    # Test to fix incorrect clusters due to dtype change
+    # (non-regression test for issue #10832)
+    X = np.array([[1, 0, 0, 0],
+                  [0, 1, 1, 0],
+                  [0, 1, 1, 0],
+                  [0, 0, 0, 1]], dtype='float32')
+    afp = AffinityPropagation(preference=1, affinity='precomputed',
+                              random_state=0).fit(X)
+    expected = np.array([0, 1, 1, 2])
+    assert_array_equal(afp.labels_, expected)
