Add dimension check to Gemv.perform. Test some cases that were incorrect.

theano/tensor/blas.py

@@ -87,6 +87,11 @@ class Gemv(Op):
         if _have_fblas:
             gemv = _blas_gemv_fns[y.dtype]
 
+            if (A.shape[0] != y.shape[0] or A.shape[1] != x.shape[0]):
+                raise ValueError('Incompatible shapes for gemv '
+                        '(beta * y + alpha * dot(A, x)). y: %s, A: %s, x: %s '
+                        % (y.shape, A.shape, x.shape))#
+
             #Here I suppose that A is in c order. If we don't make it explicitly
             #  as fortran order, scipy 0.7.2 seam to create a copy in fortran
             #  order instead of just reshaping it and using the trans flag.

theano/tensor/tests/test_blas.py

@@ -761,6 +761,23 @@ def test_gemv2():
     if config.mode != 'FAST_COMPILE':
         assert topo[-1].op.inplace==True
 
+class TestGemv(TestCase):
+    def test_gemv_dimensions(self):
+        A = T.matrix('A')
+        x, y = T.vectors('x', 'y')
+        alpha = theano.shared(1.0, name='alpha')
+        beta = theano.shared(1.0, name='beta')
+
+        z = beta * y + alpha * T.dot(A, x)
+        f = theano.function([A, x, y], z)
+
+        A_val = numpy.ones((5,3), dtype=config.floatX)
+        f(A_val, numpy.ones(3), numpy.ones(5))
+        self.assertRaises(ValueError, f, A_val, numpy.ones(4), numpy.ones(5))
+        self.assertRaises(ValueError, f, A_val, numpy.ones(3), numpy.ones(6))
+        self.assertRaises(ValueError, f, A_val, numpy.ones(4), numpy.ones(6))
+
+
 # The following gemv tests were added in March 2011 by Ian Goodfellow
 # and are based on the gemv tests from scipy
 # http://projects.scipy.org/scipy/browser/trunk/scipy/linalg/tests/test_fblas.py?rev=6803