small modif to installation doc.

doc/install.txt

@@ -23,8 +23,15 @@ to be installed:
     python >= 2.5 (2.4 should be supported as well)
         Including the development package(python-dev or python-devel on most OS)
 
+    g++, python-dev
+        Highly recommended, to compile generated C code.
+	We currently compile when we import theano. This could be moved to when we compile c code
+	to allow using theano without c code generation. If someone has the time to do it,
+	it would be welcome. We still would recommend to have them to have faster time.
+
     `numpy <http://numpy.scipy.org/>`_ >= 1.3.0
         Earlier versions have memory leaks.
+
     `SciPy <http://scipy.org>`_
         Specifically numpy, sparse, and weave. We recommend scipy
         >=0.7 if you are using sparse matrices, because scipy.sparse
@@ -36,15 +43,15 @@ to be installed:
 
 The following libraries and software are optional:
 
-    g++, python-dev
-        Highly recommended, to compile generated C code.
     `nose <http://somethingaboutorange.com/mrl/projects/nose/>`_
         Recommended, to run Theano's test-suite.
     `sphinx <http://sphinx.pocoo.org/>`_ >=0.5.1, `pygments <http://pygments.org/>`_
         Used to build documentation. latex and dvipng
         are also necessary for math to show up as images.
     `mercurial <http://www.selenic.com/mercurial/>`_
-        To download bleeding-edge version of Theano.
+        To download bleeding-edge version of Theano.	
+    `nvidia cuda driver and sdk <http://developer.nvidia.com/object/gpucomputing.html>`_
+    	Needed if you want to use the GPU. Only nvidia gpu and float32 dtype supported for now.
 
 .. _install_bleeding_edge: