IPU Integration 5/5

CHANGELOG.md

@@ -68,6 +68,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Added trainer stage hooks for Training Plugins and Accelerators ([#7864](https://github.com/PyTorchLightning/pytorch-lightning/pull/7864))
 
 
+- Added IPU Accelerator ([#7867](https://github.com/PyTorchLightning/pytorch-lightning/pull/7867))
+
+
 - Added a warning if `Trainer(log_every_n_steps)` is a value too high for the training dataloader ([#7734](https://github.com/PyTorchLightning/pytorch-lightning/pull/7734))
 
 

pl_examples/ipu_examples/mnist.py

@@ -0,0 +1,89 @@
+# Copyright The PyTorch Lightning team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import torch
+from torch.nn import functional as F
+
+import pytorch_lightning as pl
+from pl_examples.basic_examples.mnist_datamodule import MNISTDataModule
+
+
+class LitClassifier(pl.LightningModule):
+
+    def __init__(
+        self,
+        hidden_dim: int = 128,
+        learning_rate: float = 0.0001,
+    ):
+        super().__init__()
+        self.save_hyperparameters()
+
+        self.l1 = torch.nn.Linear(28 * 28, self.hparams.hidden_dim)
+        self.l2 = torch.nn.Linear(self.hparams.hidden_dim, 10)
+
+    def forward(self, x):
+        x = x.view(x.size(0), -1)
+        x = torch.relu(self.l1(x))
+        x = torch.relu(self.l2(x))
+        return x
+
+    def training_step(self, batch, batch_idx):
+        x, y = batch
+        y_hat = self(x)
+        loss = F.cross_entropy(y_hat, y)
+        return loss
+
+    def validation_step(self, batch, batch_idx):
+        x, y = batch
+        probs = self(x)
+        # we currently return the accuracy as the validation_step/test_step is run on the IPU devices.
+        # Outputs from the step functions are sent to the host device, where we calculate the metrics in
+        # validation_epoch_end and test_epoch_end for the test_step.
+        acc = self.accuracy(probs, y)
+        return acc
+
+    def test_step(self, batch, batch_idx):
+        x, y = batch
+        logits = self(x)
+        acc = self.accuracy(logits, y)
+        return acc
+
+    def accuracy(self, logits, y):
+        # currently IPU poptorch doesn't implicit convert bools to tensor
+        # hence we use an explicit calculation for accuracy here. Once fixed in poptorch
+        # we can use the accuracy metric.
+        acc = torch.sum(torch.eq(torch.argmax(logits, -1), y).to(torch.float32)) / len(y)
+        return acc
+
+    def validation_epoch_end(self, outputs) -> None:
+        # since the training step/validation step and test step are run on the IPU device
+        # we must log the average loss outside the step functions.
+        self.log('val_acc', torch.stack(outputs).mean(), prog_bar=True)
+
+    def test_epoch_end(self, outputs) -> None:
+        self.log('test_acc', torch.stack(outputs).mean())
+
+    def configure_optimizers(self):
+        return torch.optim.Adam(self.parameters(), lr=self.hparams.learning_rate)
+
+
+if __name__ == '__main__':
+    dm = MNISTDataModule(batch_size=32)
+
+    model = LitClassifier()
+
+    trainer = pl.Trainer(max_epochs=2, ipus=8)
+
+    trainer.fit(model, datamodule=dm)
+    trainer.test(model, datamodule=dm)

pytorch_lightning/accelerators/__init__.py

@@ -13,4 +13,5 @@
 from pytorch_lightning.accelerators.accelerator import Accelerator  # noqa F401
 from pytorch_lightning.accelerators.cpu import CPUAccelerator  # noqa F401
 from pytorch_lightning.accelerators.gpu import GPUAccelerator  # noqa F401
+from pytorch_lightning.accelerators.ipu import IPUAccelerator  # noqa F401
 from pytorch_lightning.accelerators.tpu import TPUAccelerator  # noqa F401

pytorch_lightning/accelerators/ipu.py

@@ -0,0 +1,35 @@
+# Copyright The PyTorch Lightning team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from collections import Callable
+from typing import Any
+
+from torch.optim import Optimizer
+
+import pytorch_lightning as pl
+from pytorch_lightning.accelerators.accelerator import Accelerator
+from pytorch_lightning.utilities.exceptions import MisconfigurationException
+
+
+class IPUAccelerator(Accelerator):
+    """ Accelerator for IPUs. """
+
+    def setup_optimizers(self, trainer: 'pl.Trainer') -> None:
+        super().setup_optimizers(trainer)
+
+        if len(self.optimizers) > 1:
+            raise MisconfigurationException("IPUs currently only support one optimizer.")
+
+    def optimizer_step(self, optimizer: Optimizer, opt_idx: int, lambda_closure: Callable, **kwargs: Any) -> None:
+        # Optimizer step is handled by the IPU accelerator.
+        lambda_closure()

pytorch_lightning/plugins/__init__.py

@@ -9,6 +9,7 @@
 from pytorch_lightning.plugins.precision.fully_sharded_native_amp import (  # noqa: F401
     FullyShardedNativeMixedPrecisionPlugin,
 )
+from pytorch_lightning.plugins.precision.ipu_precision import IPUPrecisionPlugin  # noqa: F401
 from pytorch_lightning.plugins.precision.native_amp import NativeMixedPrecisionPlugin  # noqa: F401
 from pytorch_lightning.plugins.precision.precision_plugin import PrecisionPlugin  # noqa: F401
 from pytorch_lightning.plugins.precision.sharded_native_amp import ShardedNativeMixedPrecisionPlugin  # noqa: F401
@@ -20,6 +21,7 @@
 from pytorch_lightning.plugins.training_type.dp import DataParallelPlugin  # noqa: F401
 from pytorch_lightning.plugins.training_type.fully_sharded import DDPFullyShardedPlugin  # noqa: F401
 from pytorch_lightning.plugins.training_type.horovod import HorovodPlugin  # noqa: F401
+from pytorch_lightning.plugins.training_type.ipu import IPUPlugin  # noqa: F401
 from pytorch_lightning.plugins.training_type.parallel import ParallelPlugin  # noqa: F401
 from pytorch_lightning.plugins.training_type.rpc import RPCPlugin  # noqa: F401
 from pytorch_lightning.plugins.training_type.rpc_sequential import RPCSequentialPlugin  # noqa: F401
@@ -41,6 +43,8 @@
     "DeepSpeedPrecisionPlugin",
     "DoublePrecisionPlugin",
     "HorovodPlugin",
+    "IPUPlugin",
+    "IPUPrecisionPlugin",
     "NativeMixedPrecisionPlugin",
     "PrecisionPlugin",
     "ShardedNativeMixedPrecisionPlugin",

pytorch_lightning/plugins/precision/ipu_precision.py

@@ -0,0 +1,60 @@
+# Copyright The PyTorch Lightning team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from typing import Any, Optional, Union
+
+from torch import Tensor
+from torch.nn import Module
+from torch.optim import Optimizer
+
+import pytorch_lightning as pl
+from pytorch_lightning.plugins.precision.precision_plugin import PrecisionPlugin
+from pytorch_lightning.utilities import GradClipAlgorithmType
+from pytorch_lightning.utilities.exceptions import MisconfigurationException
+
+
+class IPUPrecisionPlugin(PrecisionPlugin):
+
+    def __init__(self, precision: int) -> None:
+        super().__init__()
+        self.precision = precision
+
+    def backward(
+        self,
+        model: 'pl.LightningModule',
+        closure_loss: Tensor,
+        optimizer: Optimizer,
+        opt_idx: int,
+        should_accumulate: bool,
+        *args: Any,
+        **kwargs: Any,
+    ) -> Tensor:
+        # IPU internally manages bwd step.
+        return closure_loss
+
+    def clip_gradients(
+        self,
+        optimizer: Optimizer,
+        clip_val: Union[int, float],
+        gradient_clip_algorithm: GradClipAlgorithmType = GradClipAlgorithmType.NORM,
+        model: Optional[Module] = None
+    ) -> None:
+        """Clips the gradients"""
+        if clip_val is None:
+            return
+
+        clip_val = float(clip_val)
+        if clip_val <= 0:
+            return
+
+        raise MisconfigurationException("IPUs currently do not support clipping gradients.")