Using H2O models into Java for scoring or prediction

This sample generate a GBM model from R H2O library and then consume the model into Java for prediction.

Here is R Script to generate sample model using H2O

setwd("/tmp/resources/")
library(h2o)
h2o.init()
df = iris
h2o_df = as.h2o(df)
y = "Species"
x = c("Sepal.Length", "Sepal.Width", "Petal.Length", "Petal.Width")
model = h2o.gbm(y = y, x = x, training_frame = h2o_df)
model
h2o.download_mojo(model, get_genmodel_jar = TRUE)

Here is the Java code to use Model for prediction:

import hex.genmodel.easy.RowData;
import hex.genmodel.easy.EasyPredictModelWrapper;
import hex.genmodel.easy.prediction.*;
import hex.genmodel.MojoModel;

public class main {
    static void printIt(String message, MultinomialModelPrediction p) {
        System.out.println("");
        System.out.println(message);
        for (int i = 0; i < p.classProbabilities.length; i++) {
            if (i > 0) {
                System.out.print(",");
            }
            System.out.print(p.classProbabilities[i]);
        }
        System.out.println("");
    }
    public static void main(String[] args) throws Exception {
        EasyPredictModelWrapper model_orig = new EasyPredictModelWrapper(MojoModel.load("unzipped_orig"));
        {
            RowData row = new RowData();
            row.put("Sepal.Length", "1");
            row.put("Sepal.Width", "1");
            row.put("Petal.Length", "1");
            row.put("Petal.Width", "1");
            MultinomialModelPrediction p = model_orig.predictMultinomial(row);
            printIt("All 1s, orig", p);
        }
        {
            RowData row = new RowData();
            MultinomialModelPrediction p = model_orig.predictMultinomial(row);
            printIt("All NAs, orig", p);
        }
        {
            RowData row = new RowData();
            row.put("Sepal.Length", "1");
            row.put("sepwid", "1");
            row.put("Petal.Length", "1");
            row.put("Petal.Width", "1");

            MultinomialModelPrediction p = model_orig.predictMultinomial(row);
            printIt("Sepal width NA, orig", p);
        }
        // -------------------
        EasyPredictModelWrapper model_modified = new EasyPredictModelWrapper(MojoModel.load("unzipped_modified"));
        {
            RowData row = new RowData();
            row.put("Sepal.Length", "1");
            row.put("sepwid", "1");
            row.put("Petal.Length", "1");
            row.put("Petal.Width", "1");
            MultinomialModelPrediction p = model_modified.predictMultinomial(row);
            printIt("All 1s (with sepwid instead of Sepal.Width), modified", p);
        }
        {
            RowData row = new RowData();
            MultinomialModelPrediction p = model_modified.predictMultinomial(row);
            printIt("All NAs, modified", p);
        }
        {
            RowData row = new RowData();
            row.put("Sepal.Length", "1");
            row.put("Sepal.Width", "1");
            row.put("Petal.Length", "1");
            row.put("Petal.Width", "1");
            MultinomialModelPrediction p = model_modified.predictMultinomial(row);
            printIt("Sepal width NA (with Sepal.Width instead of sepwid), modified", p);
        }
    }
}

After the MOJO is downloaded you can see the model.ini as below:

[info]
h2o_version = 3.10.4.8
mojo_version = 1.20
license = Apache License Version 2.0
algo = gbm
algorithm = Gradient Boosting Machine
endianness = LITTLE_ENDIAN
category = Multinomial
uuid = 7712689150025610456
supervised = true
n_features = 4
n_classes = 3
n_columns = 5
n_domains = 1
balance_classes = false
default_threshold = 0.5
prior_class_distrib = [0.3333333333333333, 0.3333333333333333, 0.3333333333333333]
model_class_distrib = [0.3333333333333333, 0.3333333333333333, 0.3333333333333333]
timestamp = 2017-05-23T08:19:42.961-07:00
n_trees = 50
n_trees_per_class = 3
distribution = multinomial
init_f = 0.0
offset_column = null

[columns]
Sepal.Length
Sepal.Width
Petal.Length
Petal.Width
Species

[domains]
4: 3 d000.txt

If you decided to modify model.ini by renaming column (i.e.sepal.width to sepwid) you can do as below:

[info]
h2o_version = 3.10.4.8
mojo_version = 1.20
license = Apache License Version 2.0
algo = gbm
algorithm = Gradient Boosting Machine
endianness = LITTLE_ENDIAN
category = Multinomial
uuid = 7712689150025610456
supervised = true
n_features = 4
n_classes = 3
n_columns = 5
n_domains = 1
balance_classes = false
default_threshold = 0.5
prior_class_distrib = [0.3333333333333333, 0.3333333333333333, 0.3333333333333333]
model_class_distrib = [0.3333333333333333, 0.3333333333333333, 0.3333333333333333]
timestamp = 2017-05-23T08:19:42.961-07:00
n_trees = 50
n_trees_per_class = 3
distribution = multinomial
init_f = 0.0
offset_column = null

[columns]
Sepal.Length
SepWid
Petal.Length
Petal.Width
Species

[domains]
4: 3 d000.txt

Now we can run the Java commands to test the code as below:

$ java -cp .:h2o-genmodel.jar main

All 1s, orig
0.7998234476072545,0.15127335891610785,0.04890319347663747

All NAs, orig
0.009344361534466918,0.9813250958541073,0.009330542611425827

Sepal width NA, orig
0.7704658301004306,0.19829292017147707,0.03124124972809238

All 1s (with sepwid instead of Sepal.Width), modified
0.7998234476072545,0.15127335891610785,0.04890319347663747

All NAs, modified
0.009344361534466918,0.9813250958541073,0.009330542611425827

Sepal width NA (with Sepal.Width instead of sepwid), modified
0.7704658301004306,0.19829292017147707,0.03124124972809238

 Thats it, enjoy!!

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