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benchmarks.md

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Benchmarks

The integration_test module contains benchmarks derived from the TPC-DS, TPC-H, and TPCx-BB benchmarks. These are not official TPC benchmarks and are only intended to be used to compare relative performance between CPU and GPU and to help catch performance regressions in the plugin.

Data Generation

For each of these benchmarks, source data must be generated by a utility that can generate data at any scale factor, where the scale factor is an integer representing approximately how many gigabytes of data will be generated, with scale factor 1 meaning ~1 GB, and scale factor 1000 meaning ~1 TB, for example.

Further information on data generation can be found using the following links:

The remainder of this document is based on the TPC-DS benchmark but the steps are very similar for the other benchmarks. The main difference is that the package and class name is different for each benchmark.

Benchmark Package Class Names
TPC-DS com.nvidia.spark.rapids.tests.tpcds ConvertFiles, TpcdsLikeBench
TPC-xBB com.nvidia.spark.rapids.tests.tpcxbb ConvertFiles, TpcxbbLikeBench
TPC-H com.nvidia.spark.rapids.tests.tpch ConvertFiles, TpchLikeBench

Spark Shell

The integration test jar needs to be added to the --jars configuration option when launching the Spark shell. This jar can be found in the integration_tests/target directory after running mvn package, with a filename matching rapids-4-spark-integration-tests_2.12-*-SNAPSHOT.jar.

To run benchmarks on the GPU, the RAPIDS Accelerator for Apache Spark must also be installed, following the instructions provided in the Getting Started guide.

Converting to Parquet

Although it is possible to run benchmarks directly against the CSV data generated by the TPC data generators, it is common to convert the data to Parquet format and run benchmarks against the Parquet files instead.

The integration_test module contains code for converting the CSV data sets to Parquet.

The following commands can be entered into spark-shell to perform the conversion.

import com.nvidia.spark.rapids.tests.tpcds._
TpcdsLikeSpark.csvToParquet(spark, "/path/to/input", "/path/to/output")

Note that the code for converting CSV to Parquet does not explicitly specify the number of partitions to write, so the size of the resulting parquet files will vary depending on the value for spark.default.parallelism, which by default is based on the number of available executor cores. However, the file conversion methods accept coalesce and repartition arguments to better control the size of the partitions on a per-table basis.

Example using coalesce and repartition options to control the number and size of partitions for specific tables.

TpcdsLikeSpark.csvToParquet(spark, "/path/to/input", "/path/to/output", 
  coalesce=Map("customer_address" -> 1), repartition=Map("web_sales" -> 256))

It is also possible to use spark-submit to run the file conversion process.

$SPARK_HOME/bin/spark-submit \
    --master $SPARK_MASTER_URL \
    --jars $SPARK_RAPIDS_PLUGIN_JAR,$CUDF_JAR \
    --class com.nvidia.spark.rapids.tests.tpcds.ConvertFiles \
    $SPARK_RAPIDS_PLUGIN_INTEGRATION_TEST_JAR \
    --input /path/to/input \
    --output /path/to/output \
    --output-format parquet \
    --coalesce customer_address=1 \
    --repartition web_sales=256 inventory=128

It should also be noted that no decimal types will be output. The conversion code uses explicit schemas to ensure that decimal types are converted to floating-point types instead because the plugin does not yet support decimal types but these will be supported in a future release.

Running Benchmarks from a Spark shell

The benchmarks can be executed in two modes currently:

  • Execute the query and collect the results to the driver
  • Execute the query and write the results to disk (in Parquet, CSV, or ORC format)

The following commands can be entered into spark-shell to register the data files that the benchmark will query.

import com.nvidia.spark.rapids.tests.tpcds._
TpcdsLikeSpark.setupAllParquet(spark, "/path/to/tpcds")

The benchmark can be executed with the following syntax to execute the query and collect the results to the driver.

import com.nvidia.spark.rapids.tests._
val benchmark = new BenchmarkRunner(TpcdsLikeBench)
benchmark.collect(spark, "q5", iterations=3)

The benchmark can be executed with the following syntax to execute the query and write the results to Parquet. There are also writeCsv and writeOrc methods for writing the output to CSV or ORC files.

import com.nvidia.spark.rapids.tests._
val benchmark = new BenchmarkRunner(TpcdsLikeBench)
benchmark.writeParquet(spark, "q5", "/data/output/tpcds/q5", iterations=3)

Running Benchmarks from spark-submit

The benchmark runner has a command-line interface, allowing it to be submitted to Spark using spark-submit which can be more practical than using the Spark shell when running a series of benchmarks using automation.

Here is an example spark-submit command for running TPC-DS query 5, reading from Parquet and writing results to Parquet. The --output and --output-format arguments can be omitted to have the benchmark call collect() on the results instead.

$SPARK_HOME/bin/spark-submit \
    --master $SPARK_MASTER_URL \
    --jars $SPARK_RAPIDS_PLUGIN_JAR,$CUDF_JAR \
    --class com.nvidia.spark.rapids.tests.BenchmarkRunner \
    $SPARK_RAPIDS_PLUGIN_INTEGRATION_TEST_JAR \
    --benchmark tpcds \
    --query q5 \
    --input /raid/tpcds-3TB-parquet-largefiles \
    --input-format parquet \
    --output /raid/tpcds-output/tpcds-q5-cpu \
    --output-format parquet \
    --summary-file-prefix tpcds-q5-cpu \
    --iterations 1

Benchmark JSON Output

Each benchmark run produces a JSON file containing information about the environment and the query, including the following items:

  • Spark version
  • Spark configuration
  • Environment variables
  • Logical and physical query plan
  • SQL metrics for the executed plan
  • Timing information for each query iteration

Care should be taken to ensure that no sensitive information is captured from the environment before sharing these JSON files. Environment variables with names containing the words PASSWORD, TOKEN, or SECRET are filtered out, but this may not be sufficient to prevent leaking secrets.

Automating Benchmarks

For convenience, the benchmark.py script is provided, allowing benchmarks to be run in an automated way with multiple configurations. Example usage is provided in the documentation within the script.

Verifying Results

It is important to verify that queries actually produced the correct output, especially when comparing between CPU and GPU benchmarks. A utility is provided to help with this.

This is a simple utility that pulls results down to the driver for comparison so will only work for data sets that can fit in the driver's memory.

If data needs sorting before comparison, this is delegated to Spark before collecting the results.

Example usage from spark-shell:

val cpu = spark.read.parquet("/data/tpcxbb/q5-cpu")
val gpu = spark.read.parquet("/data/tpcxbb/q5-gpu")
import com.nvidia.spark.rapids.tests.common._
BenchUtils.compareResults(cpu, gpu, ignoreOrdering=true, epsilon=0.0001)

This will report on any differences between the two dataframes.

The verification utility can also be run using spark-submit using the following syntax.

$SPARK_HOME/bin/spark-submit \
    --master $SPARK_MASTER_URL \
    --jars $SPARK_RAPIDS_PLUGIN_JAR,$CUDF_JAR \
    --class com.nvidia.spark.rapids.tests.common.CompareResults \
    $SPARK_RAPIDS_PLUGIN_INTEGRATION_TEST_JAR \
    --input1 /path/to/result1 \
    --input2 /path/to/result2 \
    --input-format parquet

Performance Tuning

Please refer to the Tuning Guide for information on performance tuning.