added some tests case for the fusion when the fusion don't work.

theano/tensor/tests/test_opt.py

@@ -712,6 +712,7 @@ class test_fusion(unittest.TestCase):
         iyv = theano._asarray(my_init(shp,num=70),dtype='int32')
         izv = theano._asarray(my_init(shp,num=70),dtype='int32')
         fwx=fw+fx
+        ftanx = theano.tensor.tan(fx)
         cases = [
             (fx+fy+fz,(fx,fy,fz),(fxv,fyv,fzv),1,fxv+fyv+fzv,'float32'),#0
             (fx*fy*fz,(fx,fy,fz),(fxv,fyv,fzv),1,fxv*fyv*fzv,'float32'),#1
@@ -792,6 +793,12 @@ class test_fusion(unittest.TestCase):
             (theano.tensor.pow(fx*fy+fz,fx*fy),(fx,fy,fz),(fxv,fyv,fzv),1,numpy.power(fxv*fyv+fzv,fxv*fyv),'float32'),
             (fv+fy**fz,(fv,fy,fz),(fvv,fyv,fzv),2,fvv+fyv**fzv,'float32'),#fused with a dimshuffle
             (fv-fy+tanh(fz),(fv,fy,fz),(fvv,fyv,fzv),2,fvv-fyv+numpy.tanh(fzv),'float32'),#fused with a dimshuffle
+
+            # Cases where the same input is reused many times.
+            (theano.tensor.mul(fx,fx,fx,fx),(fx,),(fxv,),1,fxv*fxv*fxv*fxv,'float32'),
+            (theano.tensor.mul(fx,ftanx,ftanx),(fx,),(fxv,),2,fxv*numpy.tan(fxv)*numpy.tan(fxv),'float32'),# TODO: This case is not fused!
+            (theano.tensor.mul(fx,ftanx,ftanx,fx),(fx,),(fxv,),2,fxv*numpy.tan(fxv)*numpy.tan(fxv)*fxv,'float32'),# TODO: This case is not fused!
+            (theano.tensor.mul(ftanx,ftanx,fx+fy),(fx,fy),(fxv,fyv),3,numpy.tan(fxv)*numpy.tan(fxv)*(fxv+fyv),'float32'),# TODO: This case is not fused!
             ]
         if slice:
             cases = cases[slice]
@@ -814,7 +821,7 @@ class test_fusion(unittest.TestCase):
                 t1=time.time()
             else:
                 out=shared_fn(numpy.zeros(shp, dtype=out_dtype),'out')
-                f = function(sym_inputs,[],updates=[(out,out+g)],mode=mode)
+                f = function(sym_inputs,[],updates=[(out, g)],mode=mode)
                 t0=time.time()
                 for x in range(nb_repeat):
                     f(*val_inputs)