could not find the monitored key in the returned metrics

[morestart]

error:lightning.fabric.utilities.exceptions.MisconfigurationException: ModelCheckpoint(monitor='val_loss')could not find the monitored key in the returned metrics: ['train_loss', 'epoch', 'step']. HINT: Did you calllog('val_loss', value)in theLightningModule?
but in my code,i set val_loss key

    def training_step(self, batch, batch_idx):
        x, y = batch
        predict = self.forward(x)

        loss = lat_weighted_mae(predict, y, lat=self.lat, vars=self.vars)
        self.log(
            "train_loss",
            loss,
            on_step=True,
            on_epoch=False,
            prog_bar=True,
        )
        return loss

    def validation_step(self, batch, batch_idx):
        x, y = batch
        predict = self.forward(x)
        loss = lat_weighted_mae(predict, y, lat=self.lat, vars=self.vars)
        self.log(
            "val_loss",
            loss,
            on_step=True,
            on_epoch=False,
            prog_bar=True,
        )
        return loss

[morestart]

Remove the following content to solve the problem:

self.log(
            "val_loss",
            loss,
            on_step=True,
            on_epoch=False,
            prog_bar=True,
        )

to

self.log(
            "val_loss",
            loss,
            # on_step=True,
            # on_epoch=False,
            # prog_bar=True,
        )

[adosar]

Can you elaborate why this work?

[morestart]

The updated version should be valid

[JonasGRG]

Just had the same issue. It seems like the val_loss is not available for the checkpoint monitor when logged on step only, so it has to be logged on epoch as well. Considering doing a PR.