added documentation for the new env. var. THEANO_BASE_COMPILEDIR.

doc/install.txt

@@ -87,6 +87,16 @@ automatic code generation, but that way is much, much slower.
     compiler. It should include library names to link against for BLAS
     functions. Default: ``-lblas``.
 
+- ``THEANO_BASE_COMPILEDIR``:
+    A directory with read/write access permissions where Theano will store
+    a sub directory for each architecture for autogenerated code and C modules. 
+    Default: ``$HOME/.theano/``. The sub directory is name as 
+    ``compiledir_xxx`` where ``xxx`` is a platform identifier.
+    If this
+    directory does not exist or does not have the correct permissions,
+    Theano will try to create it with the correct permissions. If that fails,
+    an exception will be raised and no C code will be compiled.
+
 - ``THEANO_COMPILEDIR``:
     A directory with read/write access permissions where Theano will store
     autogenerated code and C modules. Default:

doc/topics/pipeline.txt

@@ -102,6 +102,7 @@ case if ``borrow`` was True, the thunk would be allowed to reuse (or
     which by default is set to ``$HOME/.theano/compiledir_xxx``, where
     ``xxx`` identifies the platform. It may be manually set to a different
     location either by setting the ``THEANO_COMPILEDIR`` environment variable,
+    the ``THEANO_BASE_COMPILEDIR`` environment variable
     or by calling ``theano.gof.compiledir.set_compiledir(..)`` within your
     Python script.