Documented convolution meta-optimizer in doc/library/tensor/nnet/conv.txt

doc/library/tensor/nnet/conv.txt

@@ -46,6 +46,16 @@
     into Theano, and an implementation by Alex Krizhevsky available via
     Pylearn2. See the documentation below on how to use them.
 
+    As of November 24th, 2014, you can also use a meta-optimizer to
+    automatically choose the fastest implementation for each specific
+    convolution in your graph. For each instance, it will compile and benchmark
+    each applicable implementation of the ones listed below and choose the
+    fastest one. As performance is dependent on input and filter shapes, this
+    only works for operations introduced via nnet.conv2d with fully specified
+    shape information.
+    Enable it via the Theano flag ``optimizer_including=conv_meta``, and
+    optionally set it to verbose mode via the flag `metaopt.verbose=1`.
+
 
 TODO: Give examples on how to use these things! They are pretty complicated.