datasets.Dataset.map too slow even with num_proc

[luckyfan-cs]

After modifying my dataset processing pipeline, the speed of datasets.Dataset.map() remains slow (40-70 examples/sec). The dataset mapping operations are as follows:

padded_dataset = dataset.map(pad_sequence, batched=True, num_proc=data_args.preprocessing_num_workers)
sp_dataset = padded_dataset.map(sp_split, batched=True, num_proc=data_args.preprocessing_num_workers)
However, the speed is still too slow even after optimizing num_proc. The expected speed is much higher.

[rank1]: RuntimeError: One of the subprocesses has abruptly died during map operation.To debug the error, disable multiprocessing.

[HaoshengZou]

1. Is your [rank1]: RuntimeError related to speed issue?
2. We tested with small data that preprocessing_num_workers=8 achieves near 8x speedup compared to not setting preprocessing_num_workers (defaults to no multiprocessing). How much speedup have you seen turning on multiprocessing with preprocessing_num_workers=??

[luckyfan-cs]

1. it is not related to the speed issue.
2. I set the Map function with num_proc=8, and initially, the progress was steady
   Map (num_proc=8): 66%|██████▋ | 68000/102561 [31:28<12:53, 44.69 examples/s]
   Map (num_proc=8): 67%|██████▋ | 69000/102561 [31:29<08:59, 62.20 examples/s]
   Map (num_proc=8): 68%|██████▊ | 70000/102561 [31:29<06:13, 87.11 examples/s]
   Map (num_proc=8): 68%|██████▊ | 70000/102561 [31:32<08:07, 66.84 examples/s]
   Map (num_proc=8): 70%|███████ | 72000/102561 [31:29<03:14, 157.17 examples/s]
   Map (num_proc=8): 69%|██████▉ | 71000/102561 [31:32<05:35, 94.03 examples/s]",

However, after some time, the process unexpectedly failed without any apparent reason. and the speed is also very slow.

[luckyfan-cs]

no report error

[luckyfan-cs]

I compared my setup with LLama Factory, and the parameters for 360-LLama-Factory are as follows:

cutoff_len: 120,000
overwrite_cache: true
preprocessing_num_workers: 16
max_new_tokens: 24,000

Map (num_proc=8): 66%|██████▋ | 68000/102561 [31:28<12:53, 44.69 examples/s]
Map (num_proc=8): 67%|██████▋ | 69000/102561 [31:29<08:59, 62.20 examples/s]
Map (num_proc=8): 68%|██████▊ | 70000/102561 [31:29<06:13, 87.11 examples/s]
Map (num_proc=8): 68%|██████▊ | 70000/102561 [31:32<08:07, 66.84 examples/s]
Map (num_proc=8): 70%|███████ | 72000/102561 [31:29<03:14, 157.17 examples/s]
Map (num_proc=8): 69%|██████▉ | 71000/102561 [31:32<05:35, 94.03 examples/s]

For the llama-factory:

dataset: open_thoughts_114k
template: qwen
cutoff_len: 24000
overwrite_cache: true
preprocessing_num_workers: 16

33%|███▎ | 474/1425 [10:12<20:30, 1.29s/it]�[A

33%|███▎ | 475/1425 [10:14<27:00, 1.71s/it]�[A

33%|███▎ | 476/1425 [10:16<27:53, 1.76s/it]�[A

33%|███▎ | 477/1425 [10:18<25:08, 1.59s/it]�[A

34%|███▎ | 478/1425 [10:18<20:27, 1.30s/it]�[A

34%|███▎ | 479/1425 [10:20<22:19, 1.42s/it]�[A

34%|███▎ | 480/1425 [10:21<18:49, 1.20s/it]�[A

There is roughly a 100x difference in processing speed between the two setups.

[gom168]

    --model_name_or_path Qwen/Qwen2.5-0.5B-Instruct \
    --preprocessing_num_workers 8 \
    --template qwen \
    --cutoff_len 120000 \
    --cache_dir .cache \
    --overwrite_cache \
    --sequence_parallel_size 2 \

Running padding split on dataset (num_proc=8): 100%|█| 6284/6284 [01:24<00:00, 74.77 examples/s]
Running padding split on dataset (num_proc=8): 100%|█| 6284/6284 [01:24<00:00, 73.95 examples/s]
Running sequence parallel split on dataset (num_proc=8): 100%|█| 6284/6284 [04:51<00:00, 21.58 examples/s]
Running sequence parallel split on dataset (num_proc=8): 100%|█| 6284/6284 [05:03<00:00, 20.71 examples/s]

We use the open source dataset Yukang/LongAlpaca-16k-length for testing. The specific settings and running results are as above. Our test results are all normal.

[HaoshengZou]

@luckyfan-cs Does your error still exist? As tested by @gom168, we haven't seen abnormal behavior on our side. If you are still experiencing it, simply let us know the minimal steps to reproduce your error. You could get in our WeChat group.

[HaoshengZou]

@luckyfan-cs The "unexpectedly fail" error should be fixed by the latest commit. Feel free to give it a try by decreasing --preprocessing_batch_size argument to 500 or 250 (default 1000).