{"record":{"id":"e41771615b97c58b","repo":"microsoft/qlib","slug":"unknown-loss-s-e41771","errorCode":null,"errorMessage":"unknown loss `%s`","messagePattern":"unknown loss `(.+?)`","errorType":"validation","errorClass":"ValueError","httpStatus":null,"severity":"error","filePath":"qlib/contrib/model/pytorch_localformer.py","lineNumber":95,"sourceCode":"\r\n        self.fitted = False\r\n        self.model.to(self.device)\r\n\r\n    @property\r\n    def use_gpu(self):\r\n        return self.device != torch.device(\"cpu\")\r\n\r\n    def mse(self, pred, label):\r\n        loss = (pred.float() - label.float()) ** 2\r\n        return torch.mean(loss)\r\n\r\n    def loss_fn(self, pred, label):\r\n        mask = ~torch.isnan(label)\r\n\r\n        if self.loss == \"mse\":\r\n            return self.mse(pred[mask], label[mask])\r\n\r\n        raise ValueError(\"unknown loss `%s`\" % self.loss)\r\n\r\n    def metric_fn(self, pred, label):\r\n        mask = torch.isfinite(label)\r\n\r\n        if self.metric in (\"\", \"loss\"):\r\n            return -self.loss_fn(pred[mask], label[mask])\r\n\r\n        raise ValueError(\"unknown metric `%s`\" % self.metric)\r\n\r\n    def train_epoch(self, x_train, y_train):\r\n        x_train_values = x_train.values\r\n        y_train_values = np.squeeze(y_train.values)\r\n\r\n        self.model.train()\r\n\r\n        indices = np.arange(len(x_train_values))\r\n        np.random.shuffle(indices)\r\n\r","sourceCodeStart":77,"sourceCodeEnd":113,"githubUrl":"https://github.com/microsoft/qlib/blob/79633dd9506ea689e5400dea0197717b5b3d74b7/qlib/contrib/model/pytorch_localformer.py#L77-L113","documentation":"LocalTransformerModel.loss_fn implements only 'mse' (masked, computed on float tensors). Any other loss string raises ValueError at the first loss computation inside fit()'s training loop.","triggerScenarios":"LocalTransformerModel(loss != 'mse') followed by fit(); the error appears on the first batch of the first epoch.","commonSituations":"Shared YAML hyperparameter blocks across models; typo'd loss names.","solutions":["Set loss='mse'","Override loss_fn in a subclass for other losses"],"exampleFix":"# before\nLocalTransformerModel(loss=\"mae\")\n\n# after\nLocalTransformerModel(loss=\"mse\")","handlingStrategy":"validation","validationCode":"assert loss == \"mse\", \"LocalTransformerModel supports only loss='mse'\"","typeGuard":"def is_supported_loss(name: str) -> bool:\n    return name == \"mse\"","tryCatchPattern":null,"preventionTips":["Pin loss='mse' for LocalTransformer","Subclass and override loss_fn for anything else"],"tags":["qlib","localformer","loss-function","invalid-argument"],"backgroundTag":null,"analyzedSha":"79633dd9506ea689e5400dea0197717b5b3d74b7","analyzedAt":"2026-08-15T07:01:27.511Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}