Merge pull request #249 from pascanur/infershape_cond_scan

theano/scan_module/scan_op.py

@@ -979,6 +979,11 @@ class Scan(PureOp):
 
         scan_outs += [x for x in
                      input_shapes[offset:offset + self.n_shared_outs]]
+        # if we are dealing with a repeat-until, then we do not know the
+        # leading dimension so we replace it for every entry with Shape_i
+        if self.as_while:
+            scan_outs = [(Shape_i(0)(o),)+x[1:]
+                         for o, x in zip(node.outputs,scan_outs)]
         return scan_outs
 
     ### GRAD FUNCTION

theano/scan_module/tests/test_scan.py

@@ -2495,8 +2495,6 @@ class T_Scan(unittest.TestCase):
         # so if it compiles it means the test pass
         f = theano.function([V, W], O)
 
-
-
     def test_while2(self):
         x = tensor.vector('x')
         def lambda_fn(x_t):
@@ -2515,6 +2513,17 @@ class T_Scan(unittest.TestCase):
                 if isinstance(x.op, theano.scan_module.scan_op.Scan)]
         assert len(lssc) == 1
 
+    def test_while_infershape(self):
+        x = tensor.vector('x')
+        def lambda_fn(x_t):
+            return x_t + 1, theano.scan_module.until( x_t > 3)
+        o, _  = theano.scan(lambda_fn, x)
+
+        f = theano.function([x], o.shape[0], mode=mode_with_opt)
+        vx = numpy.zeros((50,), dtype = theano.config.floatX)
+        vx[23] = 4
+        out = f(vx)
+        assert out == 24
 
     def test_grad_multiple_seqs_different_nsteps(self):
         # Example provided Michael Forbes