Importing H2O MOJOs from H2O-3¶
When training algorithm using Sparkling Water API, Sparkling Water always produces H2OMOJOModel
. It is however also possible
to import existing MOJO into the Sparkling Water ecosystem from H2O-3. After importing the H2O-3 MOJO the API is unified for the
loaded MOJO and the one created in Sparkling Water, for example, using H2OXGBoost
.
H2O MOJOs can be imported to Sparkling Water from all data sources supported by Apache Spark such as a local file, S3 or HDFS and the semantics of the import is the same as in the Spark API.
When creating a MOJO specified by a relative path and HDFS is enabled, the method attempts to load the MOJO from the HDFS home directory of the current user. In case we are not running on a HDFS-enabled system, we create the mojo from a current working directory.
- Scala
- Python
- R
import ai.h2o.sparkling.ml.models._
val model = H2OMOJOModel.createFromMojo("prostate_mojo.zip")
An absolute local path can also be used. To create a MOJO model from a locally available MOJO, call:
- Scala
- Python
- R
import ai.h2o.sparkling.ml.models._
val model = H2OMOJOModel.createFromMojo("/Users/peter/prostate_mojo.zip")
Absolute paths on Hadoop can also be used. To create a MOJO model from a MOJO stored on HDFS, call:
- Scala
- Python
- R
import ai.h2o.sparkling.ml.models._
val model = H2OMOJOModel.createFromMojo("/user/peter/prostate_mojo.zip")
The call loads the mojo file from the following location hdfs://{server}:{port}/user/peter/prostate_mojo.zip
, where {server}
and {port}
is automatically filled in by Spark.
We can also manually specify the type of data source we need to use, in that case, we need to provide the schema:
- Scala
- Python
- R
import ai.h2o.sparkling.ml.models._
// HDFS
val modelHDFS = H2OMOJOModel.createFromMojo("hdfs:///user/peter/prostate_mojo.zip")
// Local file
val modelLocal = H2OMOJOModel.createFromMojo("file:///Users/peter/prostate_mojo.zip")
The loaded model is an immutable instance, so it’s not possible to change the configuration of the model during its existence.
On the other hand, the model can be configured during its creation via H2OMOJOSettings
:
- Scala
- Python
- R
import ai.h2o.sparkling.ml.models._
val settings = H2OMOJOSettings(convertUnknownCategoricalLevelsToNa = true, convertInvalidNumbersToNa = true)
val model = H2OMOJOModel.createFromMojo("prostate_mojo.zip", settings)
To score the dataset using the loaded mojo, call:
- Scala
- Python
- R
model.transform(dataset)
In Scala, the createFromMojo
method returns a mojo model instance cast as a base class H2OMOJOModel
. This class holds
only properties that are shared across all MOJO model types from the following type hierarchy:
H2OMOJOModel
H2OUnsupervisedMOJOModel
H2OSupervisedMOJOModel
H2OTreeBasedSupervisedMOJOModel
If a Scala user wants to get a property specific for a given MOJO model type, he/she must utilize casting or
call the createFromMojo
method on the specific MOJO model type.
import ai.h2o.sparkling.ml.models._
val specificModel = H2OTreeBasedSupervisedMOJOModel.createFromMojo("prostate_mojo.zip")
println(s"Ntrees: ${specificModel.getNTrees()}") // Relevant only to GBM, DRF and XGBoost
Exporting the loaded MOJO model using Sparkling Water¶
To export the MOJO model, call model.write.save(path)
. In case of Hadoop enabled system, the command by default
uses HDFS.
Importing the previously exported MOJO model from Sparkling Water¶
To import the MOJO model, call H2OMOJOModel.read.load(path)
. In case of Hadoop enabled system, the command by default
uses HDFS.
Accessing additional prediction details¶
After computing predictions, the prediction
column contains in case of classification problem the predicted label
and in case regression problem the predicted number. If we need to access more details for each prediction, see the content
of a detailed prediction column. By default, the column is named named detailed_prediction
. It could contain, for example,
predicted probabilities for each predicted label in case of classification problem, Shapley values, and other information.
Customizing the MOJO Settings¶
We can configure the output and format of predictions via the H2OMOJOSettings. The available options are
predictionCol
- Specifies the name of the generated prediction column. The default value is prediction.detailedPredictionCol
- Specifies the name of the generated detailed prediction column. The detailed prediction column, if enabled, contains additional details, such as probabilities, Shapley values etc. The default value is detailed_prediction.convertUnknownCategoricalLevelsToNa
- Enables or disables conversion of unseen categoricals to NAs. By default, it is disabled.convertInvalidNumbersToNa
- Enables or disables conversion of invalid numbers to NAs. By default, it is disabled.withContributions
- Enables or disables computing Shapley values. Shapley values are generated as a sub-column for the detailed prediction column. By default, it is disabled.withLeafNodeAssignments
- When enabled, a user can obtain the leaf node assignments after the model traininig has finished. By default, it is disabled.
Methods available on MOJO Model¶
Obtaining Domain Values¶
To obtain domain values of the trained model, we can run getDomainValues()
on the model. This call
returns a mapping from a column name to its domain in a form of an array.
Obtaining Model Category¶
The method getModelCategory
can be used to get the model category (such as binomial
, multinomial
etc).
Obtaining Training Params¶
The method getTrainingParams
can be used to get a map containing all training parameters used in the H2O. It is a map
from the parameter name to the value. The parameters name use the H2O’s naming structure.
Obtaining Metrics¶
There are several methods to obtain metrics from the MOJO model. All return a map from the metric name to its double value.
getTrainingMetrics
- obtain training metricsgetValidationMetrics
- obtain validation metricsgetCrossValidationMetrics
- obtain cross validation metrics
We also have method getCurrentMetrics
which gets one of the metrics above based on the following algorithm:
If cross-validation was used, ie, setNfolds
was called and the value was higher than zero, this method returns cross-validation
metrics. If cross-validation was not used, but the validation frame was used, the method returns validation metrics. The validation
frame is used if setSplitRatio
was called with the value lower than one. If neither cross-validation nor validation frame
was used, this method returns the training metrics.
Obtaining Leaf Node Assignments¶
To obtain the leaf node assignments, please first make sure to set withLeafNodeAssignments
to true on your MOJO settings object. The leaf node assignments are now stored
in the ${detailedPredictionCol}.leafNodeAssignments
column on the dataset obtained from the prediction.
Please replace ${detailedPredictionCol}
with the actual value of your detailed prediction col. By default,
it is detailed_prediction
.