To build H2O from the repository, perform the following steps.

Recipe 1: Clone fresh, build, skip tests, and run H2O

# Build H2O
git clone https://github.com/h2oai/h2o-3.git
cd h2o-3
./gradlew build -x test

You may encounter problems: e.g. npm missing. Install it:
brew install npm

# Start H2O
java -jar build/h2o.jar

# Point browser to http://localhost:54321

Recipe 2: Clone fresh, build, and run tests (requires a working install of R)

git clone https://github.com/h2oai/h2o-3.git
cd h2o-3
./gradlew syncSmalldata
./gradlew syncRPackages
./gradlew build

Notes:

• Running tests starts five test JVMs that form an H2O cluster and requires at least 8GB of RAM (preferably 16GB of RAM).
• Running ./gradlew syncRPackages is supported on Windows, OS X, and Linux, and is strongly recommended but not required. ./gradlew syncRPackages ensures a complete and consistent environment with pre-approved versions of the packages required for tests and builds. The packages can be installed manually, but we recommend setting an ENV variable and using ./gradlew syncRPackages. To set the ENV variable, use the following format (where `${WORKSPACE} can be any path):

mkdir -p ${WORKSPACE}/Rlibrary
export R_LIBS_USER=${WORKSPACE}/Rlibrary

Recipe 3: Pull, clean, build, and run tests

git pull
./gradlew syncSmalldata
./gradlew syncRPackages
./gradlew clean
./gradlew build

Notes

• We recommend using ./gradlew clean after each git pull.

• Skip tests by adding -x test at the end the Gradle build command line. Tests typically run for 7-10 minutes on a MacBook Pro laptop with 4 CPUs (8 hyperthreads) and 16 GB of RAM.

• Syncing smalldata is not required after each pull, but if tests fail due to missing data files, then try ./gradlew syncSmalldata as the first troubleshooting step. Syncing smalldata downloads data files from AWS S3 to the smalldata directory in your workspace. The sync is incremental. Do not check in these files. The smalldata directory is in .gitignore. If you do not run any tests, you do not need the smalldata directory.

• Running ./gradlew syncRPackages is supported on Windows, OS X, and Linux, and is strongly recommended but not required. ./gradlew syncRPackages ensures a complete and consistent environment with pre-approved versions of the packages required for tests and builds. The packages can be installed manually, but we recommend setting an ENV variable and using ./gradlew syncRPackages. To set the ENV variable, use the following format (where ${WORKSPACE} can be any path):

  mkdir -p ${WORKSPACE}/Rlibrary
  export R_LIBS_USER=${WORKSPACE}/Rlibrary
  

Recipe 4: Just building the docs

./gradlew clean && ./gradlew build -x test && (export DO_FAST=1; ./gradlew dist)
open target/docs-website/h2o-docs/index.html

Recipe 5: Building using a Makefile

Root of the git repository contains a Makefile with convenient shortcuts for frequent build targets used in development. To build h2o.jar while skipping tests and also the building of alternative assemblies, execute

make

To build h2o.jar using the minimal assembly, run

make minimal

The minimal assembly is well suited for development of H2O machine learning algorithms. It doesn't bundle some heavyweight dependencies (like Hadoop) and using it saves build time as well as need to download large libraries from Maven repositories.

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