Merge pull request #1099 from nouiz/fix_crash_extract_diag

doc/library/printing.txt

@@ -129,7 +129,7 @@ shown.
 3) The function :func:`theano.printing.pydotprint` will print a compiled theano function to a png file.
 
 
-In the image, Apply nodes (the applications of ops) are shown as boxes and variables are shown as ovals.
+In the image, Apply nodes (the applications of ops) are shown as ellipses and variables are shown as boxes.
 The number at the end of each label indicates graph position.  
 Boxes and ovals have their own set of positions, so you can have apply #1 and also a
 variable #1.

theano/sandbox/linalg/ops.py

@@ -703,7 +703,7 @@ class ExtractDiag(Op):
 
         # zero-dimensional matrices ...
         if x.shape[0] == 0 or x.shape[1] == 0:
-            z[0] = numpy.zeros(0)
+            z[0] = numpy.zeros(0, dtype=x.dtype)
             return
 
         if x.shape[0] < x.shape[1]:

theano/sandbox/linalg/tests/test_linalg.py

@@ -332,6 +332,7 @@ def test_diag():
     assert ok
 
 
+# not testing the view=True case since it is not used anywhere.
 def test_extract_diag():
     rng = numpy.random.RandomState(utt.fetch_seed())
     x = theano.tensor.matrix()
@@ -370,7 +371,10 @@ def test_extract_diag_grad():
     tensor.verify_grad(extract_diag, [x], rng=rng)
 
 
-# not testing the view=True case since it is not used anywhere.
+def test_extract_diag_empty():
+    c = theano.tensor.constant(numpy.array([[], []], 'int32'))
+    extract_diag(c).eval()
+
 
 def test_trace():
     rng = numpy.random.RandomState(utt.fetch_seed())