NeMo Curator - GPU-Accelerated Data Curation

NVIDIA's toolkit for preparing high-quality training data for LLMs.

When to use NeMo Curator

Use NeMo Curator when:

• Preparing LLM training data from web scrapes (Common Crawl)
• Need fast deduplication (16× faster than CPU)
• Curating multi-modal datasets (text, images, video, audio)
• Filtering low-quality or toxic content
• Scaling data processing across GPU cluster

Performance:

• 16× faster fuzzy deduplication (8TB RedPajama v2)
• 40% lower TCO vs CPU alternatives
• Near-linear scaling across GPU nodes

Use alternatives instead:

• datatrove: CPU-based, open-source data processing
• dolma: Allen AI's data toolkit
• Ray Data: General ML data processing (no curation focus)

Quick start

Installation

bash
# NeMo Curator 1.x installs with uv. Extras use hyphens (PyPI-normalized):
#   text-cuda12 / text-cpu (and image/video/audio/math variants), or `all`.

# Text curation (CUDA 12)
uv pip install "nemo-curator[text-cuda12]"

# All modalities
uv pip install "nemo-curator[all]"

# CPU-only text (slower)
uv pip install "nemo-curator[text-cpu]"

Basic text curation pipeline

> Major version rewrite (1.x): NeMo Curator was rewritten around a Ray-based > pipeline/stage architecture. The old DocumentDataset + nemo_curator.modules.* / > ScoreFilter / Modify call-the-object-on-a-dataset API from 0.x is gone. In 1.x you > compose ProcessingStages into a Pipeline and run it with an executor. The exact > stage/import surface differs per modality — treat the examples in this skill below as > conceptual (0.x-style) and follow the current > quickstart > and text guide for the > exact 1.x APIs rather than copying imports verbatim.

Shape of a 1.x pipeline (from the upstream quickstart):

python
from nemo_curator.pipeline import Pipeline
from nemo_curator.stages.base import ProcessingStage
from nemo_curator.stages.resources import Resources
from nemo_curator.backends.xenna import XennaExecutor
from nemo_curator.core.client import RayClient

# 1. Define/compose stages (load -> filter -> dedupe -> classify -> write).
#    Each stage declares its own Resources (CPU cores, GPU memory, replicas).
pipeline = Pipeline(name="curation", stages=[...])

# 2. Run it with an executor (Ray-backed).
client = RayClient()
client.start()
pipeline.run(XennaExecutor())
client.stop()

The 0.x-style snippets in the sections that follow illustrate the concepts (quality filtering, exact/fuzzy/semantic dedup, PII redaction, classifier filtering). For runnable 1.x code, map each concept onto the corresponding stage from the modality guide.

Data curation pipeline

Stage 1: Quality filtering

python
from nemo_curator.filters import (
    WordCountFilter,
    RepeatedLinesFilter,
    UrlRatioFilter,
    NonAlphaNumericFilter
)

# Apply 30+ heuristic filters
from nemo_curator import ScoreFilter

# Word count filter
dataset = dataset.filter(WordCountFilter(min_words=50, max_words=100000))

# Remove repetitive content
dataset = dataset.filter(RepeatedLinesFilter(max_repeated_line_fraction=0.3))

# URL ratio filter
dataset = dataset.filter(UrlRatioFilter(max_url_ratio=0.2))

Stage 2: Deduplication

Exact deduplication:

python
from nemo_curator.modules import ExactDuplicates

# Remove exact duplicates
deduped = ExactDuplicates(id_field="id", text_field="text")(dataset)

Fuzzy deduplication (16× faster on GPU):

python
from nemo_curator.modules import FuzzyDuplicates

# MinHash + LSH deduplication
fuzzy_dedup = FuzzyDuplicates(
    id_field="id",
    text_field="text",
    num_hashes=260,      # MinHash parameters
    num_buckets=20,
    hash_method="md5"
)

deduped = fuzzy_dedup(dataset)

Semantic deduplication:

python
from nemo_curator.modules import SemanticDuplicates

# Embedding-based deduplication
semantic_dedup = SemanticDuplicates(
    id_field="id",
    text_field="text",
    embedding_model="sentence-transformers/all-MiniLM-L6-v2",
    threshold=0.8  # Cosine similarity threshold
)

deduped = semantic_dedup(dataset)

Stage 3: PII redaction

python
from nemo_curator.modules import Modify
from nemo_curator.modifiers import PIIRedactor

# Redact personally identifiable information
pii_redactor = PIIRedactor(
    supported_entities=["EMAIL_ADDRESS", "PHONE_NUMBER", "PERSON", "LOCATION"],
    anonymize_action="replace"  # or "redact"
)

redacted = Modify(pii_redactor)(dataset)

Stage 4: Classifier filtering

python
from nemo_curator.classifiers import QualityClassifier

# Quality classification
quality_clf = QualityClassifier(
    model_path="nvidia/quality-classifier-deberta",
    batch_size=256,
    device="cuda"
)

# Filter low-quality documents
high_quality = dataset.filter(lambda doc: quality_clf(doc["text"]) > 0.5)

GPU acceleration

GPU vs CPU performance

| Operation | CPU (16 cores) | GPU (A100) | Speedup | |-----------|----------------|------------|---------| | Fuzzy dedup (8TB) | 120 hours | 7.5 hours | 16× | | Exact dedup (1TB) | 8 hours | 0.5 hours | 16× | | Quality filtering | 2 hours | 0.2 hours | 10× |

Multi-GPU scaling

python
from nemo_curator import get_client
import dask_cuda

# Initialize GPU cluster
client = get_client(cluster_type="gpu", n_workers=8)

# Process with 8 GPUs
deduped = FuzzyDuplicates(...)(dataset)

Multi-modal curation

Image curation

python
from nemo_curator.image import (
    AestheticFilter,
    NSFWFilter,
    CLIPEmbedder
)

# Aesthetic scoring
aesthetic_filter = AestheticFilter(threshold=5.0)
filtered_images = aesthetic_filter(image_dataset)

# NSFW detection
nsfw_filter = NSFWFilter(threshold=0.9)
safe_images = nsfw_filter(filtered_images)

# Generate CLIP embeddings
clip_embedder = CLIPEmbedder(model="openai/clip-vit-base-patch32")
image_embeddings = clip_embedder(safe_images)

Video curation

python
from nemo_curator.video import (
    SceneDetector,
    ClipExtractor,
    InternVideo2Embedder
)

# Detect scenes
scene_detector = SceneDetector(threshold=27.0)
scenes = scene_detector(video_dataset)

# Extract clips
clip_extractor = ClipExtractor(min_duration=2.0, max_duration=10.0)
clips = clip_extractor(scenes)

# Generate embeddings
video_embedder = InternVideo2Embedder()
video_embeddings = video_embedder(clips)

Audio curation

python
from nemo_curator.audio import (
    ASRInference,
    WERFilter,
    DurationFilter
)

# ASR transcription
asr = ASRInference(model="nvidia/stt_en_fastconformer_hybrid_large_pc")
transcribed = asr(audio_dataset)

# Filter by WER (word error rate)
wer_filter = WERFilter(max_wer=0.3)
high_quality_audio = wer_filter(transcribed)

# Duration filtering
duration_filter = DurationFilter(min_duration=1.0, max_duration=30.0)
filtered_audio = duration_filter(high_quality_audio)

Common patterns

Web scrape curation (Common Crawl)

python
from nemo_curator import ScoreFilter, Modify
from nemo_curator.filters import *
from nemo_curator.modules import *
from nemo_curator.datasets import DocumentDataset

# Load Common Crawl data
dataset = DocumentDataset.read_parquet("common_crawl/*.parquet")

# Pipeline
pipeline = [
    # 1. Quality filtering
    WordCountFilter(min_words=100, max_words=50000),
    RepeatedLinesFilter(max_repeated_line_fraction=0.2),
    SymbolToWordRatioFilter(max_symbol_to_word_ratio=0.3),
    UrlRatioFilter(max_url_ratio=0.3),

    # 2. Language filtering
    LanguageIdentificationFilter(target_languages=["en"]),

    # 3. Deduplication
    ExactDuplicates(id_field="id", text_field="text"),
    FuzzyDuplicates(id_field="id", text_field="text", num_hashes=260),

    # 4. PII redaction
    PIIRedactor(),

    # 5. NSFW filtering
    NSFWClassifier(threshold=0.8)
]

# Execute
for stage in pipeline:
    dataset = stage(dataset)

# Save
dataset.to_parquet("curated_common_crawl/")

Distributed processing

python
from nemo_curator import get_client
from dask_cuda import LocalCUDACluster

# Multi-GPU cluster
cluster = LocalCUDACluster(n_workers=8)
client = get_client(cluster=cluster)

# Process large dataset
dataset = DocumentDataset.read_parquet("s3://large_dataset/*.parquet")
deduped = FuzzyDuplicates(...)(dataset)

# Cleanup
client.close()
cluster.close()

Performance benchmarks

Fuzzy deduplication (8TB RedPajama v2)

• CPU (256 cores): 120 hours
• GPU (8× A100): 7.5 hours
• Speedup: 16×

Exact deduplication (1TB)

• CPU (64 cores): 8 hours
• GPU (4× A100): 0.5 hours
• Speedup: 16×

Quality filtering (100GB)

• CPU (32 cores): 2 hours
• GPU (2× A100): 0.2 hours
• Speedup: 10×

Cost comparison

CPU-based curation (AWS c5.18xlarge × 10):

• Cost: $3.60/hour × 10 = $36/hour
• Time for 8TB: 120 hours
• Total: $4,320

GPU-based curation (AWS p4d.24xlarge × 2):

• Cost: $32.77/hour × 2 = $65.54/hour
• Time for 8TB: 7.5 hours
• Total: $491.55

Savings: 89% reduction ($3,828 saved)

Supported data formats

• Input: Parquet, JSONL, CSV
• Output: Parquet (recommended), JSONL
• WebDataset: TAR archives for multi-modal

Use cases

Production deployments:

• NVIDIA used NeMo Curator to prepare Nemotron-4 training data
• Open-source datasets curated: RedPajama v2, The Pile

References

• Filtering Guide - 30+ quality filters, heuristics
• Deduplication Guide - Exact, fuzzy, semantic methods

Resources

• GitHub: https://github.com/NVIDIA-NeMo/Curator
• Docs: https://docs.nvidia.com/nemo/curator/latest/
• Version: 1.2.0 (1.x is a Ray-based pipeline rewrite — see the quickstart before copying 0.x snippets)
• License: Apache 2.0