Fix problem with verify_grad for hstack, vstack and cast

theano/sparse/tests/test_sp2.py

@@ -105,17 +105,21 @@ class TestCast(utt.InferShapeTester):
                                         self.op_class)
 
     def test_grad(self):
-        # TODO Find the problem with the grad of downcast
-        # a = sp.csc_matrix(self.properties, dtype='float64')
-        # verify_grad_sparse(S2.Cast('float32'), [a], cast_to_output_type=True)
-
         for dtype in tensor.float_dtypes:
-            a = sp.csc_matrix(self.properties, dtype=dtype)
-            verify_grad_sparse(S2.Cast('float64'), [a])
+            for t in tensor.float_dtypes:
+                eps = None
+                if t == 'float32':
+                    eps = 7e-4
+                a = sp.csc_matrix(self.properties, dtype=dtype)
+                verify_grad_sparse(S2.Cast(t), [a], eps=eps)
 
         for dtype in tensor.float_dtypes:
-            a = sp.csr_matrix(self.properties, dtype=dtype)
-            verify_grad_sparse(S2.Cast('float64'), [a])
+            for t in tensor.float_dtypes:
+                eps = None
+                if t == 'float32':
+                    eps = 7e-4
+                a = sp.csr_matrix(self.properties, dtype=dtype)
+                verify_grad_sparse(S2.Cast(t), [a], eps=eps)
 
 
 class HVStackTester(utt.InferShapeTester):
@@ -161,11 +165,16 @@ class HVStackTester(utt.InferShapeTester):
     def test_grad(self):
         for format in sparse.sparse_formats:
             for out_f in sparse.sparse_formats:
-                for dtype in ['float64']:  # sparse.float_dtypes:
+                for dtype in sparse.float_dtypes:
+                    eps = None
+                    if dtype == 'float32':
+                        eps = 7e-4
+
                     verify_grad_sparse(
                         self.op_class(format=out_f, dtype=dtype),
                         self.mat[format],
-                        structured=False)
+                        structured=False,
+                        eps=eps)
 
 
 def _hv_switch(op, expected_function):