Remove a useless check. It can be a cached constant. This is safe in the…

theano/tensor/blas.py

@@ -852,9 +852,6 @@ class Gemm(GemmRelated):
                 (self, len(inputs)))
         z, a, x, y, b = inputs
 
-        # For the consistency check we don't want z to be a cached constant.
-        if getattr(z, 'cached', False):
-            z = copy.copy(z)
         zr, xr, yr = [set(view_roots(i)) for i in (z, x, y)]
 
         # We want the gemm to be inplace. When this op is inplace, it
@@ -867,10 +864,11 @@ class Gemm(GemmRelated):
         # think there is another mechanism that would prevent this,
         # but I don't what to modify old code and have chance to break
         # something.
-        if zr.intersection(xr):
-            raise InconsistencyError(Gemm.E_z_uniq, (z, x))
-        if zr.intersection(yr):
-            raise InconsistencyError(Gemm.E_z_uniq, (z, y))
+        if self.inplace:
+            if zr.intersection(xr):
+                raise InconsistencyError(Gemm.E_z_uniq, (z, x))
+            if zr.intersection(yr):
+                raise InconsistencyError(Gemm.E_z_uniq, (z, y))
 
         if z.ndim != 2:
             raise TypeError(Gemm.E_rank, z)

theano/tensor/tests/test_blas.py

@@ -105,7 +105,7 @@ class t_gemm(TestCase):
     def test0a(self):
         Gemm.debug = True
         try:
-            g = gemm_inplace([1.], 1., [1.], [1.], 1.)
+            g = gemm_no_inplace([1.], 1., [1.], [1.], 1.)
         except TypeError as e:
             if exc_message(e) is Gemm.E_rank:
                 return