Univ-Bench Artificial Data Generator (UBA)

Data Generator for the LUBM Benchmark, this is the original code for the generator rewritten to have a proper CLI and be much more scalable:

• Improvements
  • generate.sh script for launching
  • Refactor code to make it cleaner while keeping behaviour as-is
  • Use log4j for logging
  • Added support for N-Triples and Turtle format outputs
  • Added support for compressed output (GZip)
  • Use a proper command line parsing library that provides meaningful built in help and parsing errors
  • New command line options:
    • Added -o <dir>/--output <dir> option to control where generated data files are written
    • Added --format <format> option to control the output format, supports OWL, DAML, NTRIPLES, TURTLE, GRAPHML, GRAPHML_NODESFIRST, NEO4J_GRAPHML and JSON
      • The GraphML and JSON based formats are property graph encodings of the generated dataset
    • Added --compress option which compresses output files with GZip as they are generated
    • Added --consolidate <mode> option which controls how many files are generates. None generates 1 file per university department, Partial generates 1 file per university and Full generates a file per thread. Maximal tries to reduce the number of files as far as possible, exact number of files produces depends on the output format.
    • Added -t <threads>/--threads <threads> option to allow parallel data generation for better performance
    • Added --quiet option to reduce logging verbosity
    • Added --max-time <minutes> option to specify the maximum amount of time to allow data generation to run for before forcibly aborting
• Build Changes
  • Now requires Java 1.7
  • pom.xml and changed directory structure to be able to build with Maven
  • Build a shaded JAR with defined main class so the JAR can be run directly
  • Added useful dependencies
• Bug fixes
  • Use OS specific filename separator character
  • Check for errors when writing files

Building

You will need a Java 7 JDK available on the build system.

We use Apache Maven as the build tool. You will need Maven 3.x installed in order to build, Maven 3.3.0 or higher is recommended or higher is recommended. Please note that Maven automatically downloads the required build tools and dependencies from the Internet so you will need an Internet connection to build.

The build artefacts are portable so you can build on one system and then simply copy generate.sh and the target directory across to the system where you will run the generator.

Assuming all prerequisites are met the following will build the generator:

> mvn clean install

Usage

You'll need a Java 7 JRE available on the system.

> ./generate.sh options

Run the following to see the usage summary:

> ./generate.sh --help

Performance Tuning

There are a number of parameters that can be used to tune the performance of the generator. The best combination will depend on the hardware on which you are generating the data.

Multi-threading

We strongly suggest using --threads to set the number of threads, typically you should set this to twice the number of processor cores (assuming hyper-threading enabled). Using this option will give you substantially better performance than not using it.

Consolidation

Using consolidation will reduce the number of files generated though total IO will be roughly the same. With --consolidate Partial you get a file per university (which can still be a lot of files at scale) while --consolidate Full will produce a single file per-thread which provides the least number of files while still giving good parallel throughput.

Some data formats e.g. the property graph ones require producing single files in which case two pass writes are used to balance IO contention across threads. Each thread generates files which are then registered with a background thread which combines these into a final file.

There are other data formats such as N-Triples and Turtle where this additional consolidation maybe optionally enabled by setting --consolidate Maximal. When you use this is setting the generator will select an optimal consolidation mode to use for the data format in question and apply any necessary two pass consolidation.

Compression

The --compress option trades processing power for substantially reduced IO. The reduced IO is invaluable at larger scales, for example with 1000 universities and --consolidate Full the compressed N-Triples output file is 706 MB while the uncompressed output is 23 GB i.e. an approximately 32x compression ratio.

Output Format

The value given for --format controls the output data format and can have an effect on the amount of IO done and the performance.

TURTLE is the most compact format but is most expensive to produce because the reduction to prefixed name form takes extra time. NTRIPLES and OWL are typically the fastest formats to produce.

Combining Compression and Consolidation

Whether combining --consolidate and --compress is worth it will depend on whether you are using a HDD or a SSD and perhaps more importantly the amount of free disk space you have since at large scales the data generated will be in the hundreds of gigabytes range uncompressed.

For example generating data like so:

> ./generate.sh --quiet --timing -u 1000 --format NTRIPLES  --consolidate Full --threads 8

Produces the follow performance numbers (on a quad core system with 4GB JVM Heap):

Disk	--compress	Time	Total File Sizes (Approx.)
SSD	No	188s	24 GB
SSD	Yes	233s	730 MB
HDD	No	343s	24 GB
HDD	Yes	392s	730 MB

Enabling compression increases overall time taken by roughly 25% on a SSD but by only 15% on a HDD.

For generating data like so:

> ./generate.sh --quiet --timing -u 1000 --format NTRIPLES  --consolidate Partial --threads 8

Produces the follow performance numbers (on a quad core system with 4GB JVM Heap):

Disk	--compress	Time	Total File Sizes (Approx.)
SSD	No	147s	24 GB
SSD	Yes	296s	730 MB
HDD	No	427s	24 GB
HDD	Yes	407s	730 MB

Enabling compression increases overall time taken by roughly 100% on an SSD but leaves it about the same with an HDD.

For example generating data like so:

> ./generate.sh --quiet --timing -u 1000 --format NTRIPLES  --consolidate Maximal --threads 8

Produces the follow performance numbers (on a quad core system with 4GB JVM Heap):

Disk	--compress	Time	Total File Sizes (Approx.)
SSD	No	156s	24 GB
SSD	Yes	379s	706 MB

Remember that you can use the --output option to specify where the data files are generated and thus control what kind of disk the data is written to, if you fail to specify this then files are generated in your working directory i.e. where you launched the generator from.

Note that at larger scales we would recommend enabling compression regardless because otherwise you are liable to exhaust disk space.

Copyright

Original Code

The Semantic Web and Agent Technologies (SWAT) Lab, CSE Department, Lehigh University

Modified Code

Rob Vesse

Contact

Original Author

Yuanbo Guo yug2@lehigh.edu

For more information about the benchmark, visit its homepage

Related Work

GraphML extensions based upon work from https://github.com/ssrangan/GraphBench by Rangan Sukumar but adapted for parallel data generation.

This Repository

You can file issues against this repository if they are specific to this version of the data generator. While the generator here differs substantially from the original all changes have been implemented such that the data generated remains identical.

The provided compareOutput.sh script in this repository will generate data using the original code plus the rewritten code (using a variety of the supported modes and output formats) and verifies that the generated data is identical.