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Cannot load the dataset split (in streaming mode) to extract the first rows.
Error code:   StreamingRowsError
Exception:    TypeError
Message:      Couldn't cast array of type
struct<1: struct<records: int64, rows: int64, seconds: double, total_count: double>, 2: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 3: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 4: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 5: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 6: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 7: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>>
to
{'1': {'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64'), 'total_count': Value('float64')}, '2': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}, '3': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}, '4': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}, '5': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}, '6': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}}
Traceback:    Traceback (most recent call last):
                File "/src/services/worker/src/worker/utils.py", line 147, in get_rows_or_raise
                  return get_rows(
                      dataset=dataset,
                  ...<4 lines>...
                      column_names=column_names,
                  )
                File "/src/libs/libcommon/src/libcommon/utils.py", line 272, in decorator
                  return func(*args, **kwargs)
                File "/src/services/worker/src/worker/utils.py", line 127, in get_rows
                  rows_plus_one = list(itertools.islice(safe_iter(ds, dataset=dataset), rows_max_number + 1))
                File "/src/services/worker/src/worker/utils.py", line 483, in safe_iter
                  yield from ds.decode(False) if ds.features else ds
                File "/usr/local/lib/python3.14/site-packages/datasets/iterable_dataset.py", line 2951, in __iter__
                  for key, example in ex_iterable:
                                      ^^^^^^^^^^^
                File "/usr/local/lib/python3.14/site-packages/datasets/iterable_dataset.py", line 2461, in __iter__
                  for key, pa_table in self._iter_arrow():
                                       ~~~~~~~~~~~~~~~~^^
                File "/usr/local/lib/python3.14/site-packages/datasets/iterable_dataset.py", line 2486, in _iter_arrow
                  for key, pa_table in self.ex_iterable._iter_arrow():
                                       ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
                File "/usr/local/lib/python3.14/site-packages/datasets/iterable_dataset.py", line 547, in _iter_arrow
                  for key, pa_table in iterator:
                                       ^^^^^^^^
                File "/usr/local/lib/python3.14/site-packages/datasets/iterable_dataset.py", line 430, in _iter_arrow
                  for key, pa_table in self.generate_tables_fn(**gen_kwags):
                                       ~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^
                File "/usr/local/lib/python3.14/site-packages/datasets/packaged_modules/json/json.py", line 343, in _generate_tables
                  self._cast_table(pa_table, json_field_paths=json_field_paths),
                  ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.14/site-packages/datasets/packaged_modules/json/json.py", line 132, in _cast_table
                  pa_table = table_cast(pa_table, self.info.features.arrow_schema)
                File "/usr/local/lib/python3.14/site-packages/datasets/table.py", line 2378, in table_cast
                  return cast_table_to_schema(table, schema)
                File "/usr/local/lib/python3.14/site-packages/datasets/table.py", line 2312, in cast_table_to_schema
                  cast_array_to_feature(
                  ~~~~~~~~~~~~~~~~~~~~~^
                      table[name] if name in table_column_names else pa.array([None] * len(table), type=schema.field(name).type),
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                      feature,
                      ^^^^^^^^
                  )
                  ^
                File "/usr/local/lib/python3.14/site-packages/datasets/table.py", line 1861, in wrapper
                  return pa.chunked_array([func(chunk, *args, **kwargs) for chunk in array.chunks])
                                           ~~~~^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.14/site-packages/datasets/table.py", line 2068, in cast_array_to_feature
                  _c(array.field(name) if name in array_fields else null_array, subfeature)
                  ~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.14/site-packages/datasets/table.py", line 1863, in wrapper
                  return func(array, *args, **kwargs)
                File "/usr/local/lib/python3.14/site-packages/datasets/table.py", line 2068, in cast_array_to_feature
                  _c(array.field(name) if name in array_fields else null_array, subfeature)
                  ~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                File "/usr/local/lib/python3.14/site-packages/datasets/table.py", line 1863, in wrapper
                  return func(array, *args, **kwargs)
                File "/usr/local/lib/python3.14/site-packages/datasets/table.py", line 2158, in cast_array_to_feature
                  raise TypeError(f"Couldn't cast array of type\n{_short_str(array.type)}\nto\n{_short_str(feature)}")
              TypeError: Couldn't cast array of type
              struct<1: struct<records: int64, rows: int64, seconds: double, total_count: double>, 2: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 3: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 4: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 5: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 6: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>, 7: struct<missing_parent: int64, records: int64, rows: int64, seconds: double>>
              to
              {'1': {'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64'), 'total_count': Value('float64')}, '2': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}, '3': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}, '4': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}, '5': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}, '6': {'missing_parent': Value('int64'), 'records': Value('int64'), 'rows': Value('int64'), 'seconds': Value('float64')}}

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COUNT n-gram tables

Packed n-gram tables for The COUNT: Counting N-grams Unlocks Scaling on Host Memory and Training-Free Adaptation (paper, code).

Each table maps every stored n-gram history (up to five tokens of context, so n-grams through order six) to its 32 most frequent next tokens and their stupid-backoff scores. Stupid backoff scores a next token by its count after the longest matching history, divided by that history's count, and multiplies by 0.4 for each step back to a shorter history. COUNT reads these tables from CPU RAM during training and inference; nothing in them is learned.

Tables

Directory Size Corpus Use in the paper
tables/general-797gb 797.5 GB Dolma 3 pretraining corpus Training the 370M–1B COUNT models
tables/general-142gb 142.0 GB Dolma 3 pretraining corpus Smaller table swapped in at inference
tables/general-17gb 17.1 GB Dolma 3 pretraining corpus Training the 60M–190M COUNT models; smallest swap-in table
tables/math-83gb 83.4 GB Dolmino Math subset of the Dolma 3 Dolmino pool (10.66B tokens) Math domain swap
tables/biomedical-82gb 81.7 GB Health topic split of Dolma 3's olmOCR science-PDF source (95.39B tokens) Biomedical domain swap
tables/law-80gb 80.2 GB Crime-and-law topic split of Dolma 3's olmOCR science-PDF source (12.34B tokens) Law domain swap

All tables use the Dolma 2 tokenizer (allenai/dolma2-tokenizer, vocabulary 100,278), n-gram orders 1–6, and 32 next tokens per history. The general tables differ in how many histories they keep: a history is stored only if it occurs at least this many times in the corpus. Order 1 has a single row, the empty history, whose next tokens are the most frequent tokens overall; order 2 has one row per single-token history.

Table Minimum history count Histories stored, orders 1 / 2 / 3 / 4 / 5 / 6
general-797gb 265 1 / 100K / 213M / 1.04B / 1.66B / 1.52B
general-142gb 1,536 1 / 100K / 73M / 242M / 281M / 197M
general-17gb 12,319 1 / 99.7K / 18M / 35M / 28M / 15M
math-83gb 4 1 / 86K / 15M / 78M / 158M / 210M
biomedical-82gb 45 1 / 84K / 28M / 120M / 166M / 141M
law-80gb 8 1 / 83K / 25M / 108M / 161M / 151M

build_manifest.json in each directory records the full construction settings and per-order row counts. The paper's appendix describes the count extraction, including the pruning of rare n-grams applied before scoring.

Files

Each table directory holds:

  • forward_index_topk.bin: the packed table. Per order, it stores the histories sorted for binary search, their 32 next-token IDs, one 8-bit score code per candidate (scores quantized linearly per order between the smallest stored score and zero), and a mask marking empty candidate slots.
  • build_manifest.json: construction settings, per-order sizes, and the table's SHA-256.
  • SHA256SUMS: checksums for every file.

The 797 GB table is larger than a single Hugging Face file allows, so it is split into four parts. Reassemble it after downloading (this needs about 800 GB of free disk):

cat forward_index_topk.bin.part-* > forward_index_topk.bin
sha256sum -c SHA256SUMS

Usage

The COUNT code reads a table directory with olmo_core.data.count_table.CountLookup and takes it in training and evaluation as --count-table-dir. Lookups are fastest with the table on a RAM filesystem such as /dev/shm. To evaluate a trained COUNT model with a different table, pass that table's directory to eval-checkpoint; --count-mix-table-dir and --count-mix-lambda interpolate two tables' scores, which is how the paper mixes a domain table 1:3 with the general one.

hf download IanMagnusson/count-ngram-tables --repo-type dataset \
  --include "tables/general-17gb/*" --local-dir /dev/shm/count-tables

Model checkpoints that use these tables: COUNT · learned n-gram embeddings · standard transformer.

License

The tables are derived from Dolma 3 and are released under the same ODC-By license. Counts over rare contexts can reveal short fragments of the source documents.

Citation

@article{magnusson2026count,
  title   = {The {COUNT}: Counting N-grams Unlocks Scaling on Host Memory and Training-Free Adaptation},
  author  = {Magnusson, Ian and Smith, Noah A. and Koh, Pang Wei},
  journal = {arXiv preprint arXiv:2610.20456},
  year    = {2026}
}
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