NCA-GENL - Data Analysis and Visualization - Section 4.2

Understand GPU-accelerated data manipulation with cuDF and Dask.

Understand how cuDF provides a GPU-accelerated DataFrame API compatible with pandas, enabling fast in-memory data transformations without leaving the GPU. Recognise how Dask complements cuDF by parallelising workloads across multiple GPUs or nodes when a dataset exceeds single-GPU memory.

cuDFDask

Practice question for this objective

Free sampleData Analysis and Visualizationmedium

A team already runs its tabular preprocessing comfortably with cuDF on one GPU and is deciding whether a particular workload warrants moving to dask-cuDF instead. They want to base the decision on what dask-cuDF actually adds rather than on habit. Which two circumstances genuinely justify choosing dask-cuDF over single-GPU cuDF for that workload? Select TWO.

  • AThe working dataset is larger than a single GPU's memory, so the computation must be partitioned and streamed across several GPUs to complete at all. Correct
  • BThe job must scale horizontally across multiple GPUs or several nodes, distributing partitions of the frame so the aggregate memory and compute exceed one device. Correct
  • CThe dataset already fits in one GPU's memory and the priority is the lowest possible latency on a single short transformation.
  • DThe team wants column operations to execute eagerly and return materialised results immediately after each call for interactive debugging.
  • EThe workload needs a string operation that uses regular-expression backreferences, which the team expects dask-cuDF to support where single-GPU cuDF does not.
Choose dask-cuDF over single-GPU cuDF when a dataset exceeds one GPU's memory or the work must scale horizontally across multiple GPUs or nodes. Dask-cuDF earns its overhead only when scale demands it. It partitions a logical DataFrame and schedules those partitions across many GPUs, which is what enables out-of-core processing and horizontal scaling. For data that fits on one device and needs low latency, the partitioning and lazy scheduling add cost without benefit, and distribution never adds operator coverage that the underlying cuDF kernels lack.

Why A is correct: Partitioning a frame that exceeds one device's VRAM is the core reason dask-cuDF exists, letting an out-of-core dataset be processed across a cluster.

Why B is correct: Dask supplies the scheduler and partitioned execution that spread a single logical DataFrame over many workers, which plain cuDF on one GPU cannot do.

Why C is wrong: This is the case where single-GPU cuDF is preferable; Dask adds graph-building and scheduling overhead that only hurts a small low-latency job.

Why D is wrong: Eager, immediate results describe cuDF's execution model; dask-cuDF is lazy and defers work until a trigger, so wanting eagerness argues against it.

Why E is wrong: Dask-cuDF executes the same cuDF kernels per partition, so an unsupported regex feature stays unsupported; distribution changes scale, not operator coverage.

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