Slightly cleaned up registration of GPU convolution optimizers and corresponding tags

theano/sandbox/cuda/dnn.py

@@ -1087,7 +1087,7 @@ if cuda_available:
     from theano.sandbox.cuda.opt import (
         local_optimizer, gpu_optimizer, gpu_seqopt)
 
-    @register_opt('cudnn')
+    #@register_opt('cudnn')  # this optimizer is registered in opt.py instead.
     @local_optimizer([GpuConv])
     def local_conv_dnn(node):
         if not dnn_available():

theano/sandbox/cuda/opt.py

@@ -1105,12 +1105,9 @@ def local_gpu_softmax_with_bias(node):
             return [host_from_gpu(gpu_sm)]
     return False
 
-# Convolution, maxpooling
+
+# Convolution
 from theano.tensor.nnet import conv
-# We need a fixed order for the user interface.
-conv_groupopt = theano.gof.optdb.LocalGroupDB()
-conv_groupopt.__name__ = "gpu_conv_opts"
-register_opt('fast_compile', 'fast_run', 'gpu')(conv_groupopt)
 
 
 def _gpu_conv_to_fftconv(node):
@@ -1163,22 +1160,8 @@ def local_conv_fft_full(node):
         return
 
 
-@local_optimizer([GpuConv])
-def local_gpu_conv(node):
-    """
-    If cudnn is available, use it. Otherwise, use the gemm version.
-    """
-    if (isinstance(node.op, GpuConv) and
-        theano.sandbox.cuda.dnn.dnn_available()):
-        return theano.sandbox.cuda.dnn.local_conv_dnn.transform(node)
-
-    # If dnn isn't avail, the local_gpu_conv_legacy wil introduce the
-    # legacy opt. Then the local_conv_gemm will convert it to gemm
-    # opt.
-
-
 @local_optimizer([gpu_from_host, conv.ConvOp])
-def local_gpu_conv_legacy(node):
+def local_gpu_conv(node):
     """
     gpu_from_host(conv) -> gpu_conv(gpu_from_host)
 
@@ -1334,19 +1317,31 @@ def local_conv_gemm(node):
                     gpu_contiguous(kern), gpu_contiguous(img))]
 
 
-# Legacy opt first, as this is the only that move to the GPU.
-# Then fft, as disabled dy default. So if use enable it, it have prio
-# Then default, use dnn if avail
-# Then default, use gemm if dnn or fft didn't worked.
-# Normally, gemm should catch all case, so the legacy should never run.
-conv_groupopt.register('local_gpu_conv_legacy', local_gpu_conv_legacy, 0,
-                       'fast_compile', 'fast_run')
-conv_groupopt.register("conv_fft_valid", local_conv_fft_valid, 1)
-conv_groupopt.register("conv_fft_full", local_conv_fft_full, 1)
-# Use dnn if avail, so have the dnn tag to be able to disable it.
-conv_groupopt.register('local_gpu_conv', local_gpu_conv, 10,
+# First we register the optimizer that moves convolutions to the GPU.
+register_opt()(local_gpu_conv)
+
+# Then we create a group of optimizers that replace the legacy GpuConv
+# with other implementations. They are tried in a specific order so we
+# can control which ones take precedence over others.
+conv_groupopt = theano.gof.optdb.LocalGroupDB()
+conv_groupopt.__name__ = "gpu_conv_opts"
+register_opt()(conv_groupopt)
+
+# FFT gets the highest priority (lowest number), but is disabled by default.
+# It can be enabled by including 'conv_fft'.
+conv_groupopt.register('conv_fft_valid', local_conv_fft_valid, 10,
+                       'conv_fft')
+conv_groupopt.register('conv_fft_full', local_conv_fft_full, 10,
+                       'conv_fft')
+# cuDNN is the second, but only registered if cuDNN is available.
+# It can be disabled by excluding 'conv_dnn' or 'cudnn'.
+from . import dnn
+if dnn.dnn_available():
+    conv_groupopt.register('conv_dnn', dnn.local_conv_dnn, 20,
                            'fast_compile', 'fast_run', 'cudnn')
-conv_groupopt.register('local_conv_gemm', local_conv_gemm, 12,
+# The GEMM-based convolution comes last to catch all remaining cases.
+# It can be disabled by excluding 'conv_gemm'.
+conv_groupopt.register('conv_gemm', local_conv_gemm, 30,
                        'fast_compile', 'fast_run')
 
 
@@ -1500,6 +1495,7 @@ def local_convtransp3d_gemm(node):
 gpu_optimizer.register("convtransp3d_gemm", local_convtransp3d_gemm)
 
 
+# Pooling
 import theano.tensor.signal.downsample as downsample