correct number of steps

theano/scan_module/scan_op.py

@@ -1251,6 +1251,16 @@ class Scan(PureOp):
         outs = self(*inputs)
         if not isinstance(outs, (list, tuple)):
             outs = [outs]
+        if self.n_nit_sot > 0:
+            grad_steps = self.outer_nitsot_outs(outs)[0].shape[0]
+        elif self.n_sit_sot > 0:
+            grad_steps = self.outer_sitsot_outs(outs)[0].shape[0] - 1
+        elif self.n_mit_sot > 0:
+            grad_steps = self.outer_mitsot_outs(outs)[0].shape[0] +\
+                    self.mintaps[self.n_mit_mot]
+        else:
+            grad_steps = inputs[0]
+
         rval = scan_utils.reconstruct_graph(self.inputs,
                                             self.outputs)
         self_inputs = rval[0]
@@ -1426,16 +1436,14 @@ class Scan(PureOp):
             n_mitmot_inps += 2
 
         if self.truncate_gradient != -1:
-            do_steps = tensor.minimum(inputs[0], self.truncate_gradient)
-        else:
-            do_steps = inputs[0]
+            grad_steps = tensor.minimum(grad_steps, self.truncate_gradient)
 
         n_nit_sot = self.n_seqs
         inner_out_nitsot = dC_dinps_t[:self.n_seqs]
         inner_out_sitsot = dC_dinps_t[ins_pos:]
         inner_inp_sitsot = dC_dXtm1s[ins_pos - self.n_seqs:]
         outer_inp_sitsot = [
-            tensor.zeros([do_steps + 1] +
+            tensor.zeros([grad_steps + 1] +
                          [x.shape[i] for i in xrange(x.ndim)],
                          dtype = y.dtype)
             for y, x in zip(inner_inp_sitsot,
@@ -1457,7 +1465,7 @@ class Scan(PureOp):
         info['n_sit_sot'] = n_sitsot_outs
         info['n_shared_outs'] = 0
         info['n_nit_sot'] = n_nit_sot
-        info['as_while'] = self.as_while
+        info['as_while'] = False
         info['profile'] = self.profile
         info['destroy_map'] = {}
         if self.name:
@@ -1466,7 +1474,7 @@ class Scan(PureOp):
             info['name'] = None
         info['mode'] = self.mode
 
-        outer_inputs = ([do_steps] +
+        outer_inputs = ([grad_steps] +
                        outer_inp_seqs +
                        outer_inp_mitmot +
                        outer_inp_sitsot +