Fix all_gather for tpu_cores=8 (#6587)

(cherry picked from commit 983a888)

Author: ethanwharris

CHANGELOG.md

@@ -119,6 +119,29 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed LightningModule `all_gather` on cpu tensors ([#6416](https://github.com/PyTorchLightning/pytorch-lightning/pull/6416))
 
 
+- Fixed when Train loop config was run during `Trainer.predict` ([#6541](https://github.com/PyTorchLightning/pytorch-lightning/pull/6541))
+
+
+- Fixed duplicate logs appearing in console when using the python logging module ([#5509](https://github.com/PyTorchLightning/pytorch-lightning/pull/5509), [#6275](https://github.com/PyTorchLightning/pytorch-lightning/pull/6275))
+
+
+- Disabled batch transfer in DP mode ([#6093](https://github.com/PyTorchLightning/pytorch-lightning/pull/6093))
+
+
+- Expose DeepSpeed loss parameters to allow users to fix loss instability ([#6115](https://github.com/PyTorchLightning/pytorch-lightning/pull/6115)
+
+
+
+## [1.2.5] - 2021-03-23
+
+### Changed
+
+
+### Fixed
+
+- Fixed a bug where `all_gather` would not work correctly with `tpu_cores=8` ([#6587](https://github.com/PyTorchLightning/pytorch-lightning/pull/6587))
+
+
 ## [1.2.4] - 2021-03-16
 
 ### Changed
@@ -139,9 +162,6 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed when Train loop config was run during `Trainer.predict` ([#6541](https://github.com/PyTorchLightning/pytorch-lightning/pull/6541))
 
 
-- Fixed when Train loop config was run during `Trainer.predict` ([#6541](https://github.com/PyTorchLightning/pytorch-lightning/pull/6541))
-
-
 ## [1.2.3] - 2021-03-09
 
 ### Fixed
@@ -180,9 +200,6 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed error thrown when using valid distributed mode in multi node ([#6297](https://github.com/PyTorchLightning/pytorch-lightning/pull/6297)
 
 
-- Fixed duplicate logs appearing in console when using the python logging module ([#5509](https://github.com/PyTorchLightning/pytorch-lightning/pull/5509), [#6275](https://github.com/PyTorchLightning/pytorch-lightning/pull/6275))
-
-
 ## [1.2.1] - 2021-02-23
 
 ### Fixed
@@ -192,12 +209,6 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed error message for AMP + CPU incompatibility ([#6107](https://github.com/PyTorchLightning/pytorch-lightning/pull/6107))
 
 
-- Disabled batch transfer in DP mode ([#6093](https://github.com/PyTorchLightning/pytorch-lightning/pull/6093))
-
-
-- Expose DeepSpeed loss parameters to allow users to fix loss instability ([#6115](https://github.com/PyTorchLightning/pytorch-lightning/pull/6115)
-
-
 ## [1.2.0] - 2021-02-18
 
 ### Added

pytorch_lightning/accelerators/tpu.py

@@ -35,12 +35,12 @@ def all_gather(self, tensor: Union[torch.Tensor], group: Optional[Any] = None, s
         Function to gather a tensor from several distributed processes
         Args:
             tensor: tensor of shape (batch, ...)
-            group: the process group to gather results from. Defaults to all processes (world)
-            sync_grads: flag that allows users to synchronize gradients for all_gather op
+            group: not available with TPUs
+            sync_grads: not available with TPUs
         Return:
             A tensor of shape (world_size, batch, ...)
         """
         # todo: Add support for backward with all_gather
-        if torch.distributed.is_initialized():
-            return xm.all_gather(tensor, group=group, sync_grads=sync_grads)
+        if isinstance(self.training_type_plugin, TPUSpawnPlugin) and self.training_type_plugin.is_distributed:
+            return xm.all_gather(tensor).view(-1, *tensor.shape)
         return tensor