Removes need to unsqueeze from dp

CHANGELOG.md

@@ -23,6 +23,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ### Changed
 
+- On DP and DDP2 unsqueeze is automated now ([#1319](https://github.com/PyTorchLightning/pytorch-lightning/pull/1319))
 - Enhanced load_from_checkpoint to also forward params to the model ([#1307](https://github.com/PyTorchLightning/pytorch-lightning/pull/1307))
 - Made `evalaute` method private >> `Trainer._evaluate(...)`. ([#1260](https://github.com/PyTorchLightning/pytorch-lightning/pull/1260))
 

pl_examples/basic_examples/lightning_module_template.py

@@ -111,10 +111,6 @@ def training_step(self, batch, batch_idx):
         # calculate loss
         loss_val = self.loss(y, y_hat)
 
-        # in DP mode (default) make sure if result is scalar, there's another dim in the beginning
-        if self.trainer.use_dp or self.trainer.use_ddp2:
-            loss_val = loss_val.unsqueeze(0)
-
         tqdm_dict = {'train_loss': loss_val}
         output = OrderedDict({
             'loss': loss_val,
@@ -145,11 +141,6 @@ def validation_step(self, batch, batch_idx):
         if self.on_gpu:
             val_acc = val_acc.cuda(loss_val.device.index)
 
-        # in DP mode (default) make sure if result is scalar, there's another dim in the beginning
-        if self.trainer.use_dp or self.trainer.use_ddp2:
-            loss_val = loss_val.unsqueeze(0)
-            val_acc = val_acc.unsqueeze(0)
-
         output = OrderedDict({
             'val_loss': loss_val,
             'val_acc': val_acc,

pl_examples/domain_templates/gan.py

@@ -99,10 +99,7 @@ def training_step(self, batch, batch_idx, optimizer_idx):
         if optimizer_idx == 0:
             # sample noise
             z = torch.randn(imgs.shape[0], self.hparams.latent_dim)
-
-            # match gpu device (or keep as cpu)
-            if self.on_gpu:
-                z = z.cuda(imgs.device.index)
+            z = z.type_as(imgs)
 
             # generate images
             self.generated_imgs = self(z)
@@ -115,8 +112,7 @@ def training_step(self, batch, batch_idx, optimizer_idx):
             # ground truth result (ie: all fake)
             # put on GPU because we created this tensor inside training_loop
             valid = torch.ones(imgs.size(0), 1)
-            if self.on_gpu:
-                valid = valid.cuda(imgs.device.index)
+            valid = valid.type_as(imgs)
 
             # adversarial loss is binary cross-entropy
             g_loss = self.adversarial_loss(self.discriminator(self.generated_imgs), valid)
@@ -134,15 +130,13 @@ def training_step(self, batch, batch_idx, optimizer_idx):
 
             # how well can it label as real?
             valid = torch.ones(imgs.size(0), 1)
-            if self.on_gpu:
-                valid = valid.cuda(imgs.device.index)
+            valid = valid.type_as(imgs)
 
             real_loss = self.adversarial_loss(self.discriminator(imgs), valid)
 
             # how well can it label as fake?
             fake = torch.zeros(imgs.size(0), 1)
-            if self.on_gpu:
-                fake = fake.cuda(imgs.device.index)
+            fake = fake.type_as(fake)
 
             fake_loss = self.adversarial_loss(
                 self.discriminator(self.generated_imgs.detach()), fake)
@@ -174,9 +168,7 @@ def train_dataloader(self):
 
     def on_epoch_end(self):
         z = torch.randn(8, self.hparams.latent_dim)
-        # match gpu device (or keep as cpu)
-        if self.on_gpu:
-            z = z.cuda(self.last_imgs.device.index)
+        z = z.type_as(self.last_imgs)
 
         # log sampled images
         sample_imgs = self(z)

pl_examples/domain_templates/reinforse_learn_Qnet.py

@@ -277,9 +277,6 @@ def training_step(self, batch: Tuple[torch.Tensor, torch.Tensor], nb_batch) -> O
         # calculates training loss
         loss = self.dqn_mse_loss(batch)
 
-        if self.trainer.use_dp or self.trainer.use_ddp2:
-            loss = loss.unsqueeze(0)
-
         if done:
             self.total_reward = self.episode_reward
             self.episode_reward = 0

pl_examples/full_examples/imagenet/imagenet_example.py

@@ -46,12 +46,6 @@ def training_step(self, batch, batch_idx):
         loss_val = F.cross_entropy(output, target)
         acc1, acc5 = self.__accuracy(output, target, topk=(1, 5))
 
-        # in DP mode (default) make sure if result is scalar, there's another dim in the beginning
-        if self.trainer.use_dp or self.trainer.use_ddp2:
-            loss_val = loss_val.unsqueeze(0)
-            acc1 = acc1.unsqueeze(0)
-            acc5 = acc5.unsqueeze(0)
-
         tqdm_dict = {'train_loss': loss_val}
         output = OrderedDict({
             'loss': loss_val,
@@ -69,12 +63,6 @@ def validation_step(self, batch, batch_idx):
         loss_val = F.cross_entropy(output, target)
         acc1, acc5 = self.__accuracy(output, target, topk=(1, 5))
 
-        # in DP mode (default) make sure if result is scalar, there's another dim in the beginning
-        if self.trainer.use_dp or self.trainer.use_ddp2:
-            loss_val = loss_val.unsqueeze(0)
-            acc1 = acc1.unsqueeze(0)
-            acc5 = acc5.unsqueeze(0)
-
         output = OrderedDict({
             'val_loss': loss_val,
             'val_acc1': acc1,

pytorch_lightning/overrides/data_parallel.py

@@ -163,6 +163,9 @@ def _worker(i, module, input, kwargs, device=None):
 
                 else:
                     output = module.validation_step(*input, **kwargs)
+
+                if module.use_dp or module.use_ddp2:
+                    auto_squeeze_dim_zeros(output)
                 # ---------------
 
             with lock:
@@ -199,3 +202,15 @@ def _worker(i, module, input, kwargs, device=None):
             raise output
         outputs.append(output)
     return outputs
+
+
+def auto_squeeze_dim_zeros(output):
+    """
+    In DP or DDP2 we need to unsqueeze dim 0
+    :param output:
+    :return:
+    """
+    for k, v in output.items():
+        is_scalar = len(v.size()) == 0
+        if is_scalar:
+            output[k] = output[k].unsqueeze(0)