Remove obsolete (and not linked) documentation on floatX.

doc/library/floatX.txt

-
-.. _libdoc_floatX:
-
-=======================================================================
-:mod:`floatX` -- Switching Between 'float32' and 'float64'
-=======================================================================
-
-.. module:: floatX
-   :platform: Unix, Windows
-   :synopsis: easy switching between float32 and float64
-.. moduleauthor:: LISA
-
-
-Guide
-=====
-
-On the CPU, 'float32' computations are often twice as fast as 'float64'
-and are half the size.
-On GPUs the speed difference between 'float32'``  and 'float64' is much greater.
-Often we develop our code using double-precision expressions, and then wonder if
-we might get the same answer much more quickly with single-precision arithmetic.
-If we have used ``tensor.dmatrix`` and ``tensor.dvector`` and so on throughout
-our code, it could be tedious to switch to single-precision Variables.  To make
-switching precisions easier, Theano provides the ``floatX`` module.
-
->>> from theano.floatX import xmatrix, xvector, xtensor4
->>> import numpy
->>> a = xvector('a')
->>> b = xmatrix()
->>> c = xtensor4()
-
-These calls are identical to ``dvector``, ``dmatrix``, and ``dtensor4`` by default, but a
-single environment variable can switch them to ``fvector``, ``fmatrix`` and ``ftensor4``.
-
-You can set the floatX precision via ``floatX`` in the :envvar:`THEANO_FLAGS`.
-It defaults to ``'float64'``. To set it to ``'float32'`` in *bash* for example, type ``export THEANO_FLAGS=floatX=float64``.
-To set it from within your program call :func:`set_floatX`
-
-The current floatX precision is stored in ``theano.config.floatX`` as a string.
-Its value is either 'float32' or 'float64'. 
-So it is easy to allocate a numpy vector of the floatX dtype.
-
->>> import theano.config as config
->>> print config.floatX   # either 'float32' or 'float64'
->>> x = numpy.asarray([1,2,3], dtype=config.floatX)
-
-Reference
-==========
-
-.. function:: xscalar(name=None)
-
-    Alias for either :func:`dscalar` or :func:`fscalar`
-
-.. function:: xvector(name=None)
-
-    Alias for either :func:`dvector` or :func:`fvector`
-
-.. function:: xmatrix(name=None)
-
-    Alias for either :func:`dmatrix` or :func:`fmatrix`
-
-.. function:: xrow(name=None)
-
-    Alias for either :func:`drow` or :func:`frow`
-
-.. function:: xcol(name=None)
-
-    Alias for either :func:`dcol` or :func:`fcol`
-
-.. function:: xtensor3(name=None)
-
-    Alias for either :func:`dtensor3` or :func:`ftensor3`
-
-.. function:: xtensor4(name=None)
-
-    Alias for either :func:`dtensor4` or :func:`ftensor4`
-
-.. function:: set_floatX(dtype=config.floatX)
-
-    Reset the :func:`xscalar`, ... :func:`xtensor4` aliases to return Variables with given dtype.
-    This is called at import-time when setting floatX in :envvar:`THEANO_FLAGS`.
-
-
-