Add option for float16 storage convolution by default.

theano/configdefaults.py

@@ -345,8 +345,9 @@ AddConfigVar('dnn.conv.algo_bwd_filter',
 AddConfigVar('dnn.conv.precision',
              "Default data precision to use for the computation in cuDNN "
              "convolutions (defaults to the same dtype as the inputs of the "
-             "convolutions).",
-             EnumStr('as_input', 'float16', 'float32', 'float64'),
+             "convolutions, or float32 if inputs are float16).",
+             EnumStr('as_input_f32', 'as_input', 'float16', 'float32',
+                     'float64'),
              in_c_key=False)
 
 

theano/gpuarray/dnn.py

@@ -888,8 +888,12 @@ def dnn_conv(img, kerns, border_mode='valid', subsample=(1, 1),
     # Establish dtype in which to perform the computation of the convolution
     if precision is None:
         precision = theano.config.dnn.conv.precision
-    if precision == 'as_input':
-        precision = theano.scalar.upcast(img.dtype, kerns.dtype)
+    if precision == 'as_input' or precision == 'as_input_f32':
+        nprec = theano.scalar.upcast(img.dtype, kerns.dtype)
+        if nprec == 'float16' and precision == 'as_input_f32':
+            precision = 'float32'
+        else:
+            precision = nprec
 
     if workmem is not None:
         if algo is not None: