如何在 pytorch-lightning 中使用 TensorBoard 记录器转储混淆矩阵？

官方文档 https://pytorch-lightning.readthedocs.io/en/0.8.3/metrics.html#tensormetric仅状态

>>> from pytorch_lightning.metrics import ConfusionMatrix
>>> target = torch.tensor([1, 1, 0, 0])
>>> preds = torch.tensor([0, 1, 0, 0])
>>> confmat = ConfusionMatrix(num_classes=2)
>>> confmat(preds, target)

这没有展示如何在框架中使用该指标。

我的尝试（方法不完整，仅显示相关部分）：

def __init__(...):
    self.val_confusion = pl.metrics.classification.ConfusionMatrix(num_classes=self._config.n_clusters)

def validation_step(self, batch, batch_index):
    ...
    log_probs = self.forward(orig_batch)
    loss = self._criterion(log_probs, label_batch)
   
    self.val_confusion.update(log_probs, label_batch)
    self.log('validation_confusion_step', self.val_confusion, on_step=True, on_epoch=False)

def validation_step_end(self, outputs):
    return outputs

def validation_epoch_end(self, outs):
    self.log('validation_confusion_epoch', self.val_confusion.compute())

在第 0 个纪元之后，这给出

    Traceback (most recent call last):
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\trainer.py", line 521, in train
        self.train_loop.run_training_epoch()
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\training_loop.py", line 588, in run_training_epoch
        self.trainer.run_evaluation(test_mode=False)
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\trainer.py", line 613, in run_evaluation
        self.evaluation_loop.log_evaluation_step_metrics(output, batch_idx)
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\evaluation_loop.py", line 346, in log_evaluation_step_metrics
        self.__log_result_step_metrics(step_log_metrics, step_pbar_metrics, batch_idx)
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\evaluation_loop.py", line 350, in __log_result_step_metrics
        cached_batch_pbar_metrics, cached_batch_log_metrics = cached_results.update_logger_connector()
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\connectors\logger_connector\epoch_result_store.py", line 378, in update_logger_connector
        batch_log_metrics = self.get_latest_batch_log_metrics()
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\connectors\logger_connector\epoch_result_store.py", line 418, in get_latest_batch_log_metrics
        batch_log_metrics = self.run_batch_from_func_name("get_batch_log_metrics")
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\connectors\logger_connector\epoch_result_store.py", line 414, in run_batch_from_func_name
        results = [func(include_forked_originals=False) for func in results]
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\connectors\logger_connector\epoch_result_store.py", line 414, in <listcomp>
        results = [func(include_forked_originals=False) for func in results]
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\connectors\logger_connector\epoch_result_store.py", line 122, in get_batch_log_metrics
        return self.run_latest_batch_metrics_with_func_name("get_batch_log_metrics",
*args, **kwargs)
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\connectors\logger_connector\epoch_result_store.py", line 115, in run_latest_batch_metrics_with_func_name
        for dl_idx in range(self.num_dataloaders)
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\connectors\logger_connector\epoch_result_store.py", line 115, in <listcomp>
        for dl_idx in range(self.num_dataloaders)
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\trainer\connectors\logger_connector\epoch_result_store.py", line 100, in get_latest_from_func_name
        results.update(func(*args, add_dataloader_idx=add_dataloader_idx, **kwargs))
      File "C:\code\EPMD\Kodex\Templates\Testing\venv\lib\site-packages\pytorch_lightning\core\step_result.py", line 298, in get_batch_log_metrics
        result[dl_key] = self[k]._forward_cache.detach()
    AttributeError: 'NoneType' object has no attribute 'detach'

                                                      

它确实在训练前通过了健全性验证检查。

失败发生在返回时validation_step_end。对我来说没什么意义。

使用指标的完全相同的方法可以很好地准确地工作。

如何得到正确的混淆矩阵？

对于闪电>=2.0.0 已过时

您可以使用以下方式报告该数字self.logger.experiment.add_figure(*tag*, *figure*).

变量self.logger.experiment实际上是一个SummaryWriter（来自 PyTorch，而不是 Lightning）。这个类有方法add_figure (文档 https://pytorch.org/docs/stable/tensorboard.html#torch.utils.tensorboard.writer.SummaryWriter.add_figure).

您可以按如下方式使用它：（MNIST 示例）

    def validation_step(self, batch, batch_idx):
        x, y = batch
        preds = self(x)
        loss = F.nll_loss(preds, y)
        return { 'loss': loss, 'preds': preds, 'target': y}

    def validation_epoch_end(self, outputs):
        preds = torch.cat([tmp['preds'] for tmp in outputs])
        targets = torch.cat([tmp['target'] for tmp in outputs])
        confusion_matrix = pl.metrics.functional.confusion_matrix(preds, targets, num_classes=10)

        df_cm = pd.DataFrame(confusion_matrix.numpy(), index = range(10), columns=range(10))
        plt.figure(figsize = (10,7))
        fig_ = sns.heatmap(df_cm, annot=True, cmap='Spectral').get_figure()
        plt.close(fig_)
        
        self.logger.experiment.add_figure("Confusion matrix", fig_, self.current_epoch)