Fix extra scan discovered by example in gh-3663. This revert 50c3fd00.

theano/scan_module/scan_op.py

@@ -1607,28 +1607,32 @@ class Scan(PureOp):
         inner_ins_shapes = []
         out_equivalent = OrderedDict()
 
+        # The two following blocks are commented as it cause in some
+        # cases extra scans in the graph. See gh-XXX for the
+        # investigation.
+
         # We skip the first outer input as it is the total or current number
         # of iterations.
         # sequences
         seqs_shape = [x[1:] for x in input_shapes[1:1 + self.n_seqs]]
-        inner_seqs = self.inputs[:self.n_seqs]
-        outer_seqs = node.inputs[1:1 + self.n_seqs]
-        for in_s, out_s in izip(inner_seqs, outer_seqs):
-            out_equivalent[in_s] = out_s[0]
+        # inner_seqs = self.inputs[:self.n_seqs]
+        # outer_seqs = node.inputs[1:1 + self.n_seqs]
+        # for in_s, out_s in izip(inner_seqs, outer_seqs):
+        #     out_equivalent[in_s] = out_s[0]
 
         # mit_mot, mit_sot, sit_sot
-        outer_inp_idx = 1 + self.n_seqs
-        inner_inp_idx = self.n_seqs
+        # outer_inp_idx = 1 + self.n_seqs
+        # inner_inp_idx = self.n_seqs
         n_outs = self.n_mit_mot + self.n_mit_sot + self.n_sit_sot
         outs_shape = []
         for idx in xrange(n_outs):
-            mintap = abs(min(self.tap_array[idx]))
+            # mintap = abs(min(self.tap_array[idx]))
             for k in self.tap_array[idx]:
                 outs_shape += [input_shapes[idx + self.n_seqs + 1][1:]]
-                corresponding_tap = node.inputs[outer_inp_idx][mintap + k]
-                out_equivalent[self.inputs[inner_inp_idx]] = corresponding_tap
-                inner_inp_idx += 1
-            outer_inp_idx += 1
+                # corresponding_tap = node.inputs[outer_inp_idx][mintap + k]
+                # out_equivalent[self.inputs[inner_inp_idx]] = corresponding_tap
+                # inner_inp_idx += 1
+            # outer_inp_idx += 1
 
         # shared_outs
         offset = 1 + self.n_seqs + n_outs

theano/scan_module/tests/test_scan_opt.py

@@ -212,7 +212,9 @@ class TestPushOutScanOutputDot(object):
         # not be the result of a Dot
         scan_node = [node for node in f_opt.maker.fgraph.toposort()
                      if isinstance(node.op, Scan)][0]
-        assert len(scan_node.op.outputs) == 1
+        # NOTE: WHEN INFER_SHAPE IS REENABLED, BELLOW THE SCAN MUST
+        # HAVE ONLY 1 OUTPUT.
+        assert len(scan_node.op.outputs) == 2
         assert not isinstance(scan_node.op.outputs[0], T.Dot)
 
         # Ensure that the function compiled with the optimization produces