add ranking integration test (#57)

Author: shuttie

.gitattributes

@@ -3,3 +3,4 @@
 *.so filter=lfs diff=lfs merge=lfs -text
 *.dll filter=lfs diff=lfs merge=lfs -text
 *.dylib filter=lfs diff=lfs merge=lfs -text
+*.gz filter=lfs diff=lfs merge=lfs -text

src/test/java/io/github/metarank/lightgbm4j/RankingIntegrationTest.java

@@ -0,0 +1,112 @@
+package io.github.metarank.lightgbm4j;
+
+import org.junit.jupiter.api.Test;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+import java.util.stream.Collectors;
+import java.util.zip.GZIPInputStream;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class RankingIntegrationTest {
+    @Test
+    public void testLetor() throws LGBMException, IOException {
+        LGBMDataset train = datasetFromResource("/mq2008/train.txt.gz", null);
+        LGBMDataset test = datasetFromResource("/mq2008/test.txt.gz", train);
+        LGBMBooster booster = LGBMBooster.create(train, "objective=lambdarank metric=ndcg lambdarank_truncation_level=10 max_depth=5 learning_rate=0.1 num_leaves=8");
+        booster.addValidData(test);
+        for (int i=0; i<100; i++) {
+            booster.updateOneIter();
+            double[] eval1 = booster.getEval(0);
+            double[] eval2 = booster.getEval(1);
+            System.out.println("train " + eval1[0] + " test " + eval2[0]);
+            assertTrue(eval1[0] > 0.5);
+        }
+        String[] names = booster.getFeatureNames();
+        double[] weights = booster.featureImportance(0, LGBMBooster.FeatureImportanceType.GAIN);
+        assertTrue(names.length > 0);
+        assertTrue(weights.length > 0);
+        booster.close();
+        train.close();
+        test.close();
+    }
+
+
+    private static LGBMDataset datasetFromResource(String file, LGBMDataset parent) throws LGBMException, IOException {
+        BufferedReader reader = new BufferedReader(new InputStreamReader(new GZIPInputStream(RankingIntegrationTest.class.getResourceAsStream(file))));
+        ArrayList<String> lines = reader.lines().map(line -> {
+            int commentIndex = line.indexOf('#');
+            if (commentIndex >= 0) {
+                return line.substring(0, commentIndex);
+            } else {
+                return line;
+            }
+        }).collect(Collectors.toCollection(ArrayList::new));
+        int maxFeatureId = 0; // features are 1-indexed!
+        Set<Integer> queriesSet = new HashSet<>();
+        for (String line: lines) {
+            String[] tokens = line.split(" ");
+            int group = Integer.parseInt(tokens[1].split(":")[1]);
+            queriesSet.add(group);
+            for (int i = 2; i < tokens.length; i++) {
+                String[] parts = tokens[i].split(":");
+                int featureId = Integer.parseInt(parts[0]);
+                if (featureId > maxFeatureId) {
+                    maxFeatureId = featureId;
+                }
+            }
+        }
+
+        int rows = lines.size();
+        int queries = queriesSet.size();
+        double[] features = new double[maxFeatureId * rows];
+        float[] labels = new float[rows];
+        int[] groups = new int[queries];
+        String[] featureNames = new String[maxFeatureId];
+        for (int i=1; i <= maxFeatureId; i++) {
+            featureNames[i-1] = "f"+i;
+        }
+        int lastGroup = Integer.MIN_VALUE;
+        int lastCount = 0;
+        int groupIndex = 0;
+        for (int row = 0; row < rows; row++) {
+            String line = lines.get(row);
+            String[] tokens = line.split(" ");
+            float label = Float.parseFloat(tokens[0]);
+            labels[row] = label;
+            int group = Integer.parseInt(tokens[1].split(":")[1]);
+            if (group != lastGroup) {
+                // next query
+                if (lastCount > 0) {
+                    // so it's not the first one
+                    groups[groupIndex] = lastCount;
+                    groupIndex++;
+                }
+                lastGroup = group;
+                lastCount = 1;
+            } else {
+                lastCount++;
+            }
+
+            for (int i=2; i < tokens.length; i++) {
+                String[] feature = tokens[i].split(":");
+                int id = Integer.parseInt(feature[0]) - 1;
+                double value = Double.parseDouble(feature[1]);
+                features[row * maxFeatureId + id] = value;
+            }
+        }
+        groups[groupIndex] = lastCount;
+
+
+        reader.close();
+        LGBMDataset dataset = LGBMDataset.createFromMat(features, rows, maxFeatureId, true, "", parent);
+        dataset.setFeatureNames(featureNames);
+        dataset.setField("label", labels);
+        dataset.setField("group", groups);
+        return dataset;
+    }
+
+}

src/test/resources/mq2008/test.txt.gz

@@ -0,0 +1,3 @@
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+size 345457

src/test/resources/mq2008/train.txt.gz

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+size 1126873