Title: Parallelize builder configs creation
State: closed

For datasets with lots of configs defined in YAML

E.g. `load_dataset("uonlp/CulturaX", "fr", revision="refs/pr/6")` from >1min to 15sec

Comments: <details>
<summary>Show benchmarks</summary>

PyArrow==8.0.0

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.005905 / 0.011353 (-0.005448) | 0.003623 / 0.011008 (-0.007385) | 0.079616 / 0.038508 (0.041108) | 0.059840 / 0.023109 (0.036730) | 0.392281 / 0.275898 (0.116383) | 0.434539 / 0.323480 (0.111059) | 0.004746 / 0.007986 (-0.003239) | 0.002935 / 0.004328 (-0.001394) | 0.062907 / 0.004250 (0.058657) | 0.048233 / 0.037052 (0.011181) | 0.394170 / 0.258489 (0.135681) | 0.427430 / 0.293841 (0.133589) | 0.027382 / 0.128546 (-0.101164) | 0.007890 / 0.075646 (-0.067756) | 0.259681 / 0.419271 (-0.159591) | 0.044085 / 0.043533 (0.000552) | 0.388640 / 0.255139 (0.133501) | 0.412665 / 0.283200 (0.129465) | 0.021256 / 0.141683 (-0.120427) | 1.485672 / 1.452155 (0.033518) | 1.531410 / 1.492716 (0.038694) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.220346 / 0.018006 (0.202340) | 0.425329 / 0.000490 (0.424840) | 0.006224 / 0.000200 (0.006024) | 0.000208 / 0.000054 (0.000153) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.024864 / 0.037411 (-0.012547) | 0.072925 / 0.014526 (0.058399) | 0.083711 / 0.176557 (-0.092845) | 0.144213 / 0.737135 (-0.592923) | 0.084201 / 0.296338 (-0.212137) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.399467 / 0.215209 (0.184258) | 3.978979 / 2.077655 (1.901325) | 1.916994 / 1.504120 (0.412874) | 1.753098 / 1.541195 (0.211903) | 1.809866 / 1.468490 (0.341376) | 0.506806 / 4.584777 (-4.077971) | 3.051044 / 3.745712 (-0.694668) | 2.857624 / 5.269862 (-2.412237) | 1.872033 / 4.565676 (-2.693644) | 0.058543 / 0.424275 (-0.365732) | 0.006569 / 0.007607 (-0.001038) | 0.472630 / 0.226044 (0.246586) | 4.724862 / 2.268929 (2.455934) | 2.413068 / 55.444624 (-53.031556) | 2.046910 / 6.876477 (-4.829567) | 2.190455 / 2.142072 (0.048383) | 0.595228 / 4.805227 (-4.210000) | 0.125942 / 6.500664 (-6.374722) | 0.059474 / 0.075469 (-0.015995) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 1.235927 / 1.841788 (-0.605861) | 17.367803 / 8.074308 (9.293495) | 13.550362 / 10.191392 (3.358970) | 0.131664 / 0.680424 (-0.548760) | 0.016331 / 0.534201 (-0.517870) | 0.331295 / 0.579283 (-0.247988) | 0.367641 / 0.434364 (-0.066723) | 0.382595 / 0.540337 (-0.157742) | 0.540361 / 1.386936 (-0.846575) |

</details>
PyArrow==latest

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.006120 / 0.011353 (-0.005233) | 0.003691 / 0.011008 (-0.007318) | 0.062768 / 0.038508 (0.024259) | 0.058045 / 0.023109 (0.034936) | 0.443616 / 0.275898 (0.167718) | 0.473854 / 0.323480 (0.150374) | 0.004710 / 0.007986 (-0.003275) | 0.002915 / 0.004328 (-0.001414) | 0.062922 / 0.004250 (0.058672) | 0.048557 / 0.037052 (0.011505) | 0.446136 / 0.258489 (0.187647) | 0.479235 / 0.293841 (0.185394) | 0.028704 / 0.128546 (-0.099842) | 0.008170 / 0.075646 (-0.067477) | 0.068853 / 0.419271 (-0.350419) | 0.041393 / 0.043533 (-0.002140) | 0.444683 / 0.255139 (0.189544) | 0.466607 / 0.283200 (0.183407) | 0.020890 / 0.141683 (-0.120793) | 1.473745 / 1.452155 (0.021590) | 1.498772 / 1.492716 (0.006055) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.216875 / 0.018006 (0.198868) | 0.411700 / 0.000490 (0.411211) | 0.003337 / 0.000200 (0.003137) | 0.000079 / 0.000054 (0.000024) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.027054 / 0.037411 (-0.010357) | 0.080617 / 0.014526 (0.066092) | 0.091052 / 0.176557 (-0.085505) | 0.144126 / 0.737135 (-0.593009) | 0.090123 / 0.296338 (-0.206216) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.461132 / 0.215209 (0.245922) | 4.598662 / 2.077655 (2.521008) | 2.539213 / 1.504120 (1.035093) | 2.362782 / 1.541195 (0.821587) | 2.428648 / 1.468490 (0.960157) | 0.506305 / 4.584777 (-4.078472) | 3.091132 / 3.745712 (-0.654581) | 2.884870 / 5.269862 (-2.384992) | 1.880806 / 4.565676 (-2.684870) | 0.058727 / 0.424275 (-0.365548) | 0.006452 / 0.007607 (-0.001155) | 0.533519 / 0.226044 (0.307474) | 5.346406 / 2.268929 (3.077478) | 2.987920 / 55.444624 (-52.456704) | 2.667591 / 6.876477 (-4.208885) | 2.848696 / 2.142072 (0.706623) | 0.601018 / 4.805227 (-4.204209) | 0.124929 / 6.500664 (-6.375735) | 0.061583 / 0.075469 (-0.013886) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 1.356825 / 1.841788 (-0.484962) | 17.964503 / 8.074308 (9.890195) | 14.691471 / 10.191392 (4.500079) | 0.132525 / 0.680424 (-0.547899) | 0.018061 / 0.534201 (-0.516140) | 0.335459 / 0.579283 (-0.243824) | 0.378260 / 0.434364 (-0.056104) | 0.390681 / 0.540337 (-0.149657) | 0.547030 / 1.386936 (-0.839906) |

</details>
</details>

![](https://cml.dev/watermark.png#8c55213a6c5fcff9b3dacce491caa68eacebe10d "CML watermark")
_The documentation is not available anymore as the PR was closed or merged._<details>
<summary>Show benchmarks</summary>

PyArrow==8.0.0

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.006624 / 0.011353 (-0.004729) | 0.004039 / 0.011008 (-0.006970) | 0.085862 / 0.038508 (0.047354) | 0.077183 / 0.023109 (0.054074) | 0.319132 / 0.275898 (0.043234) | 0.350818 / 0.323480 (0.027338) | 0.004122 / 0.007986 (-0.003864) | 0.003395 / 0.004328 (-0.000934) | 0.065237 / 0.004250 (0.060987) | 0.056675 / 0.037052 (0.019623) | 0.321040 / 0.258489 (0.062551) | 0.362011 / 0.293841 (0.068170) | 0.030988 / 0.128546 (-0.097559) | 0.008623 / 0.075646 (-0.067023) | 0.289433 / 0.419271 (-0.129839) | 0.052755 / 0.043533 (0.009222) | 0.323291 / 0.255139 (0.068152) | 0.340110 / 0.283200 (0.056911) | 0.026299 / 0.141683 (-0.115383) | 1.509405 / 1.452155 (0.057250) | 1.559993 / 1.492716 (0.067277) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.233285 / 0.018006 (0.215279) | 0.451633 / 0.000490 (0.451143) | 0.009954 / 0.000200 (0.009754) | 0.000098 / 0.000054 (0.000043) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.029623 / 0.037411 (-0.007788) | 0.083942 / 0.014526 (0.069416) | 0.097378 / 0.176557 (-0.079178) | 0.152630 / 0.737135 (-0.584506) | 0.098379 / 0.296338 (-0.197959) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.386237 / 0.215209 (0.171028) | 3.850805 / 2.077655 (1.773150) | 1.896032 / 1.504120 (0.391912) | 1.729746 / 1.541195 (0.188551) | 1.867831 / 1.468490 (0.399341) | 0.481496 / 4.584777 (-4.103281) | 3.564432 / 3.745712 (-0.181280) | 3.336084 / 5.269862 (-1.933777) | 2.040944 / 4.565676 (-2.524732) | 0.057247 / 0.424275 (-0.367028) | 0.007275 / 0.007607 (-0.000332) | 0.464600 / 0.226044 (0.238556) | 4.648562 / 2.268929 (2.379634) | 2.394430 / 55.444624 (-53.050195) | 2.029748 / 6.876477 (-4.846728) | 2.280975 / 2.142072 (0.138902) | 0.619073 / 4.805227 (-4.186154) | 0.150504 / 6.500664 (-6.350160) | 0.061206 / 0.075469 (-0.014263) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 1.267309 / 1.841788 (-0.574479) | 19.062725 / 8.074308 (10.988417) | 14.192565 / 10.191392 (4.001173) | 0.162908 / 0.680424 (-0.517515) | 0.018445 / 0.534201 (-0.515756) | 0.392110 / 0.579283 (-0.187173) | 0.415340 / 0.434364 (-0.019024) | 0.456783 / 0.540337 (-0.083554) | 0.653019 / 1.386936 (-0.733917) |

</details>
PyArrow==latest

<details>
<summary>Show updated benchmarks!</summary>

### Benchmark: benchmark_array_xd.json

| metric | read_batch_formatted_as_numpy after write_array2d | read_batch_formatted_as_numpy after write_flattened_sequence | read_batch_formatted_as_numpy after write_nested_sequence | read_batch_unformated after write_array2d | read_batch_unformated after write_flattened_sequence | read_batch_unformated after write_nested_sequence | read_col_formatted_as_numpy after write_array2d | read_col_formatted_as_numpy after write_flattened_sequence | read_col_formatted_as_numpy after write_nested_sequence | read_col_unformated after write_array2d | read_col_unformated after write_flattened_sequence | read_col_unformated after write_nested_sequence | read_formatted_as_numpy after write_array2d | read_formatted_as_numpy after write_flattened_sequence | read_formatted_as_numpy after write_nested_sequence | read_unformated after write_array2d | read_unformated after write_flattened_sequence | read_unformated after write_nested_sequence | write_array2d | write_flattened_sequence | write_nested_sequence |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.006995 / 0.011353 (-0.004358) | 0.004027 / 0.011008 (-0.006981) | 0.064124 / 0.038508 (0.025616) | 0.076004 / 0.023109 (0.052895) | 0.401760 / 0.275898 (0.125862) | 0.432339 / 0.323480 (0.108859) | 0.005471 / 0.007986 (-0.002515) | 0.003335 / 0.004328 (-0.000993) | 0.064164 / 0.004250 (0.059913) | 0.058101 / 0.037052 (0.021048) | 0.401698 / 0.258489 (0.143209) | 0.436033 / 0.293841 (0.142192) | 0.032789 / 0.128546 (-0.095757) | 0.008482 / 0.075646 (-0.067165) | 0.070707 / 0.419271 (-0.348565) | 0.048287 / 0.043533 (0.004755) | 0.395501 / 0.255139 (0.140362) | 0.419385 / 0.283200 (0.136186) | 0.024043 / 0.141683 (-0.117640) | 1.503310 / 1.452155 (0.051156) | 1.562160 / 1.492716 (0.069444) |

### Benchmark: benchmark_getitem\_100B.json

| metric | get_batch_of\_1024\_random_rows | get_batch_of\_1024\_rows | get_first_row | get_last_row |
|--------|---|---|---|---|
| new / old (diff) | 0.227629 / 0.018006 (0.209623) | 0.457306 / 0.000490 (0.456816) | 0.005835 / 0.000200 (0.005635) | 0.000109 / 0.000054 (0.000054) |

### Benchmark: benchmark_indices_mapping.json

| metric | select | shard | shuffle | sort | train_test_split |
|--------|---|---|---|---|---|
| new / old (diff) | 0.032991 / 0.037411 (-0.004420) | 0.093265 / 0.014526 (0.078739) | 0.106595 / 0.176557 (-0.069961) | 0.158557 / 0.737135 (-0.578578) | 0.106805 / 0.296338 (-0.189533) |

### Benchmark: benchmark_iterating.json

| metric | read 5000 | read 50000 | read_batch 50000 10 | read_batch 50000 100 | read_batch 50000 1000 | read_formatted numpy 5000 | read_formatted pandas 5000 | read_formatted tensorflow 5000 | read_formatted torch 5000 | read_formatted_batch numpy 5000 10 | read_formatted_batch numpy 5000 1000 | shuffled read 5000 | shuffled read 50000 | shuffled read_batch 50000 10 | shuffled read_batch 50000 100 | shuffled read_batch 50000 1000 | shuffled read_formatted numpy 5000 | shuffled read_formatted_batch numpy 5000 10 | shuffled read_formatted_batch numpy 5000 1000 |
|--------|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 0.436573 / 0.215209 (0.221364) | 4.355777 / 2.077655 (2.278122) | 2.323151 / 1.504120 (0.819031) | 2.164101 / 1.541195 (0.622906) | 2.252808 / 1.468490 (0.784318) | 0.494902 / 4.584777 (-4.089875) | 3.615073 / 3.745712 (-0.130639) | 3.329738 / 5.269862 (-1.940124) | 2.059137 / 4.565676 (-2.506539) | 0.058384 / 0.424275 (-0.365891) | 0.007330 / 0.007607 (-0.000277) | 0.512326 / 0.226044 (0.286281) | 5.125652 / 2.268929 (2.856724) | 2.861981 / 55.444624 (-52.582644) | 2.500172 / 6.876477 (-4.376305) | 2.715862 / 2.142072 (0.573789) | 0.597299 / 4.805227 (-4.207928) | 0.134346 / 6.500664 (-6.366318) | 0.060396 / 0.075469 (-0.015074) |

### Benchmark: benchmark_map_filter.json

| metric | filter | map fast-tokenizer batched | map identity | map identity batched | map no-op batched | map no-op batched numpy | map no-op batched pandas | map no-op batched pytorch | map no-op batched tensorflow |
|--------|---|---|---|---|---|---|---|---|---|
| new / old (diff) | 1.353771 / 1.841788 (-0.488017) | 19.334801 / 8.074308 (11.260493) | 14.669875 / 10.191392 (4.478483) | 0.167607 / 0.680424 (-0.512817) | 0.019839 / 0.534201 (-0.514362) | 0.395473 / 0.579283 (-0.183810) | 0.419822 / 0.434364 (-0.014542) | 0.471400 / 0.540337 (-0.068938) | 0.648297 / 1.386936 (-0.738639) |

</details>
</details>

![](https://cml.dev/watermark.png#d5a112e7f1ce1635725773d911c825adca7bcfe0 "CML watermark")
@mariosasko let me know what you think or if you have better ideas to make it fasterYea lazy data files resolution seems a better approach actually