Improve error message. (#275)

* Improve error message.

* Formatting.

open_lm/main.py

@@ -843,10 +843,14 @@ def main(args):
         expected_steps = data["train"].dataloader.num_batches
         if steps_done_epoch < (1 - args.data_tolerate_error_p) * expected_steps and not done_training:
             num_ckpt_too_few_tokens += 1
+            if is_master(args):
+                logging.warning(
+                    f"Epoch {epoch}, tokens seen: {steps_done_epoch * args.global_batch_size * args.seq_len}, tokens expected: {expected_steps * args.global_batch_size * args.seq_len}, ratio: {steps_done_epoch / expected_steps}"
+                )
 
         if num_ckpt_too_few_tokens > args.data_tolerate_num_ckpts:
             raise RuntimeError(
-                f"{num_ckpt_too_few_tokens} checkpoints happened where the number of tokens seen was less than {1 - args.data_tolerate_error_p} of expected. This is likely due to transient errors e.g. reading from S3."
+                f"{num_ckpt_too_few_tokens} checkpoints happened where the number of tokens seen was {1 - args.data_tolerate_error_p} of expected. This is likely due to transient errors e.g. reading from S3."
             )
 
         epoch = epoch + 1