udf-benchmark

name	udf-benchmark
description	Assists with benchmarking and profiling the performance of an Apache Spark UDF on the GPU. This is step 3 of 3 in the UDF conversion workflow (udf-gen-test -> udf-convert-to-* -> udf-benchmark). Use this skill when you have a CPU UDF and a RapidsUDF or SQL implementation, and need to benchmark the performance of the CPU UDF against the GPU implementation.
metadata	{"spdx-file-copyright-text":"Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.","upstream":{"model":"inherit"},"category":"data","source":{"repository":"https://github.com/NVIDIA/cudf-spark","path":"skills/udf-benchmark","license_path":"LICENSE","commit":"a707353465abe170e486d91304944c98f64fd938"}}

UDF Benchmark

Workflow

• Step 1: Implement BenchUtils (fill in TODO methods)
• Step 2: Validate with a small dataset
• Step 3: Generate full benchmark data and run benchmarks
• Step 4: cuDF microbenchmarks (skip for SQL targets)

Before making any edits, create a visible TODO checklist for every workflow step in this skill and keep it updated. Do not produce a final answer until every required checklist item is marked complete.

Prerequisites

• Project directory from Steps 1-2 (udf-gen-test, udf-convert-to-*) with passing tests

Derive <CamelName> and <snake_name> from the UDF class name.

Note: Commands require access to /tmp (Spark temp storage) and /dev (GPU device). If commands fail due to sandbox restrictions, re-run them unsandboxed.

Step 1: Implement BenchUtils

Read src/main/scala/com/udf/bench/BenchUtils.scala. Replace placeholders with the actual camel/snake UDF name.

Fill in the TODO methods following the docstrings. For variable-length inputs, generate sizable rows representative of enterprise-scale data. Refer to the unit test for schema and example data.

Step 2: Validate

Make scripts executable:

chmod +x *.sh

Run validation mode to test with a small dataset:

./run_gen_data.sh --rows 1000 --validate

This runs both the CPU and GPU implementations on the dataset. If validation fails, analyze the error and fix the BenchUtils implementation.

Step 3: Generate Data and Run Benchmarks

The scripts set the default heap size to 16g in .mvn/jvm.config; adjust depending on data size.

Generate benchmark data (10M rows):

./run_gen_data.sh --rows 10000000

Run benchmarks:

# CPU benchmark
./run_spark_benchmark.sh --mode cpu --data-path data/bench_data_10000000_rows.parquet

# GPU benchmark
./run_spark_benchmark.sh --mode gpu --data-path data/bench_data_10000000_rows.parquet

Results are saved to the results/ directory as JSON files.

Step 4: cuDF Microbenchmarks

Skip this step for SQL targets. This only applies to cuDF RapidsUDF conversions.

Follow CUDF_MICROBENCHMARKS.md to implement and run in-memory microbenchmarks.

Output

Upon successful completion:

• Benchmark utilities: src/main/scala/com/udf/bench/BenchUtils.scala
• Microbenchmarks (cuDF): src/main/scala/com/udf/bench/MicroBenchRunner.scala
• Generated data: data/
• Benchmark results: results/