create a new flag init_gpu_device that select the gpu to use, but don't…

theano/__init__.py

@@ -78,7 +78,7 @@ import scalar
 import gradient
 import gof
 
-if config.device.startswith('gpu'):
+if config.device.startswith('gpu') or config.init_gpu_device.startswith('gpu'):
     import theano.sandbox.cuda
 
 ## import scalar_opt

theano/configdefaults.py

@@ -18,10 +18,15 @@ AddConfigVar('floatX',
 #gpu mean let the driver select the gpu. Needed in case of gpu in exclusive mode.
 #gpuX mean use the gpu number X.
 AddConfigVar('device',
-        "Default device for computations",
+        "Default device for computations. If gpu, try to move computation to it when possible.",
         EnumStr('cpu', 'gpu',*['gpu%i'%i for i in range(4)])
         )
 
+AddConfigVar('init_gpu_device',
+        "Gpu device to use for computations, but don't automatically try to move the computation to this device. Usefull to run the test on a specific gpu.",
+        EnumStr('', *['gpu%i'%i for i in range(4)])
+        )
+
 AddConfigVar('force_device',
         "Raise an error if we can't use the specified device",
         BoolParam(False)

theano/sandbox/cuda/__init__.py

@@ -130,7 +130,7 @@ if cuda_available:
     import cuda_ndarray
 
 
-def use(device, force=False):
+def use(device, force=False, move_to_gpu_automatically = True):
     global cuda_enabled, cuda_initialization_error_message
     if force and not cuda_available and device.startswith('gpu'):
         raise EnvironmentError("You forced use of device %s, but CUDA initialization failed "
@@ -172,6 +172,7 @@ def use(device, force=False):
 
     elif use.device_number != device:
         _logger.warning("WARNING: ignoring call to use(%s), GPU number %i is already in use." %(str(device), use.device_number))
+    if move_to_gpu_automatically:
         optdb.add_tags('gpu',
                        'fast_run',
                        'inplace')
@@ -201,3 +202,6 @@ def handle_shared_float32(tf):
 
 if config.device.startswith('gpu'):
     use(config.device, config.force_device)
+elif config.init_gpu_device:
+    print "Will init the gpu to use a specific gpu device. This don't move automatically cpu code to gpu. For that try the theano flags device."
+    use(config.init_gpu_device, config.force_device, False)