fixed some doc strings

doc/library/config.txt

@@ -225,6 +225,20 @@ import theano and print the config variable, as in:
 
     If True, we will print extra scan debug information.
 
+.. attribute:: cycle_detection
+
+    String value, either ``regular`` or ``fast```
+
+    Default: ``regular``
+
+    If :attr:`cycle_detection` is set to ``regular``, most inplaces are allowed,
+    but it is slower. If :attr:`cycle_detection` is set to ``faster``,
+    less inplaces are allowed, but it makes the compilation faster.
+
+    The interaction of which one give the lower peak memory usage is complicated and
+    not predictable, so if you are close to the peak memory usage, triyng both
+    could give you a small gain.
+
 .. attribute:: openmp
 
     Bool value: either ``True`` or ``False``

theano/configdefaults.py

@@ -1477,11 +1477,19 @@ AddConfigVar('compile.wait',
              """Time to wait before retrying to aquire the compile lock.""",
              IntParam(5, lambda i: i > 0, allow_override=False),
              in_c_key=False)
+"""
+If cycle_detection is set to regular, most inplaces are allowed,
+but it is slower. If cycle_detection is set to faster,
+less inplaces are allowed, but it makes the compilation faster.
 
+The interaction of which one give the lower peak memory usage is complicated and
+not predictable, so if you are close to the peak memory usage, triyng both
+could give you a small gain.
+"""
 AddConfigVar('cycle_detection',
              """If true it disables the cycle detection in graph.
              """,
-             EnumStr('topo', 'fast'),
+             EnumStr('regular', 'fast'),
              in_c_key=False)
 
 

theano/gof/destroyhandler.py

@@ -425,7 +425,6 @@ class DestroyHandler(toolbox.Bookkeeper):  # noqa
 
         For now:
         - Destroyed variables can have only 1 clients.
-        - Allow sequence of destroy variables.
         - Allow view to have multiple clients.
         - Allow sequence of view.
         - But don't allow to destroy view