remove Assert condition that are always true and remove Assert op that are always true. +test.

theano/tensor/opt.py

@@ -660,6 +660,26 @@ class Assert(T.Op):
     
 assert_ = Assert()
 
+@register_specialize
+@gof.local_optimizer([Assert])
+def local_remove_useless_assert(node):
+    if isinstance(node.op, Assert):
+        cond=[]
+        for c in node.inputs[1:]:
+            try:
+                const = get_constant_value(c)
+                
+                if 0!=const.ndim or const==0:
+                    #Should we raise an error here? How to be sure it is not catched?
+                    cond.append(c)
+            except TypeError:
+                cond.append(c)
+        
+        if len(cond)==0:
+            return [node.inputs[0]]
+        if len(cond)!=len(node.inputs)-1:
+            return [assert_(node.inputs[0],*cond)]
+
 @gof.local_optimizer([T.Alloc])
 def local_alloc_elemwise(node):
     """
@@ -730,10 +750,9 @@ def local_alloc_elemwise(node):
     return [node.op(*new)]
 
 #TODO, T.eq if both input are the same, remove!
-#TODO, op that check the condition are all true and remove the Assert. Also remove the constant condition.
 #TODO, global optimizer that lift the assert to the beginning of the graph.
 #TODO, var.tag.shape to propagate the shape and lower the overhead of this op
-#TODO, when all can be optimizer do all except one
+#TODO, when all inputs can be optimized do all except one
 
 theano.configparser.AddConfigVar('experimental.local_alloc_elemwise',
         "If True enable the experimental optimization local_alloc_elemwise",

theano/tensor/tests/test_opt.py

@@ -1093,6 +1093,51 @@ class test_assert(unittest.TestCase):
         f(1,1)
         self.failUnlessRaises(AssertionError, f, 1,0)
 
+    def test1(self):
+        #remove assert that are always true
+        mode = theano.config.mode
+        if mode == 'FAST_COMPILE':
+            mode = 'FAST_RUN'
+        mode = compile.mode.get_mode(mode)
+
+        x=T.scalar()
+        f = theano.function([x],theano.tensor.opt.assert_(x,1),mode=mode)
+        assert f(1)==1
+        assert f(5)==5
+        topo=f.maker.env.toposort()
+        assert len(topo)==0
+
+    def test2(self):
+        #remove assert condition that are always true
+        mode = theano.config.mode
+        if mode == 'FAST_COMPILE':
+            mode = 'FAST_RUN'
+        mode = compile.mode.get_mode(mode)
+
+        x=T.scalar()
+        y=T.scalar()
+        f = theano.function([x,y],theano.tensor.opt.assert_(x,y,1),mode=mode)
+        assert f(1,1)==1
+        assert f(5,1)==5
+        topo=f.maker.env.toposort()
+        assert len(topo)==1
+        assert len(topo[0].inputs)==2
+
+    def test3(self):
+        #don't remove assert condition that are always false
+        mode = theano.config.mode
+        if mode == 'FAST_COMPILE':
+            mode = 'FAST_RUN'
+        mode = compile.mode.get_mode(mode)
+
+        x=T.scalar()
+        y=T.scalar()
+        f = theano.function([x,y],theano.tensor.opt.assert_(x,y,0),mode=mode)
+        self.failUnlessRaises(AssertionError, f, 1,0)
+        topo=f.maker.env.toposort()
+        assert len(topo)==1
+        assert len(topo[0].inputs)==3
+
 def test_local_mul_specialize():
 
     # test a few cases to make sure that the basics are covered