Some more improvements

src/main/java/org/apache/sysds/hops/rewriter/RewriterRule.java

@@ -386,6 +386,7 @@ public List<RewriterRule> createNonGenericRules(Map<String, Set<String>> funcMap
 	static class IdentityRewriterStatement {
 		public RewriterStatement stmt;
 
+		@Deprecated
 		public IdentityRewriterStatement(RewriterStatement stmt) {
 			this.stmt = stmt;
 		}

src/main/java/org/apache/sysds/hops/rewriter/RewriterUtils.java

@@ -1149,7 +1149,7 @@ private static List<RewriterStatement> generateSubtrees(RewriterStatement stmt,
 		// Scan if operand is not a DataType
 		List<Integer> indices = new ArrayList<>();
 		for (int i = 0; i < stmt.getOperands().size(); i++) {
-			if (stmt.getOperands().get(i).isInstruction() || stmt.isLiteral())
+			if (stmt.getChild(i).isInstruction() || stmt.getChild(i).isLiteral())
 				indices.add(i);
 		}
 
@@ -1165,6 +1165,8 @@ private static List<RewriterStatement> generateSubtrees(RewriterStatement stmt,
 
 		List<List<RewriterStatement>> mOptions = indices.stream().map(i -> generateSubtrees(stmt.getOperands().get(i), visited, ctx, maxCombinations)).collect(Collectors.toList());
 		List<RewriterStatement> out = new ArrayList<>();
+		//System.out.println("Stmt: " + stmt.toParsableString(ctx));
+		//System.out.println("mOptions: " + mOptions);
 
 		for (int subsetMask = 0; subsetMask < totalSubsets; subsetMask++) {
 			List<List<RewriterStatement>> mOptionCpy = new ArrayList<>(mOptions);
@@ -1178,6 +1180,7 @@ private static List<RewriterStatement> generateSubtrees(RewriterStatement stmt,
 				}
 			}
 
+			//System.out.println("mOptionCopy: " + mOptionCpy);
 			out.addAll(mergeSubtreeCombinations(stmt, indices, mOptionCpy, ctx, maxCombinations));
 			if (out.size() > maxCombinations) {
 				System.out.println("Aborting early due to too many combinations");

src/test/java/org/apache/sysds/test/component/codegen/rewrite/RewriterClusteringTest.java

@@ -82,7 +82,7 @@ public void testExpressionClustering() {
 		db.parForEach(expr -> {
 			if (ctr.incrementAndGet() % 10 == 0)
 				System.out.println("Done: " + ctr.intValue() + " / " + size);
-			if (ctr.intValue() > 2000)
+			if (ctr.intValue() > 10000)
 				return; // Skip
 			// First, build all possible subtrees
 			//System.out.println("Eval:\n" + expr.toParsableString(ctx, true));
@@ -140,7 +140,7 @@ public void testExpressionClustering() {
 			totalCanonicalizationMillis.addAndGet(mCanonicalizationMillis);
 		});
 
-		printEquivalences(foundEquivalences, System.currentTimeMillis() - startTime, generatedExpressions.longValue(), evaluatedExpressions.longValue(), totalCanonicalizationMillis.longValue(), failures.longValue(), true);
+		printEquivalences(/*foundEquivalences*/ Collections.emptyList(), System.currentTimeMillis() - startTime, generatedExpressions.longValue(), evaluatedExpressions.longValue(), totalCanonicalizationMillis.longValue(), failures.longValue(), true);
 
 		System.out.println("===== SUGGESTED REWRITES =====");
 		List<Tuple5<Double, Long, Long, RewriterStatement, RewriterStatement>> rewrites = findSuggestedRewrites(foundEquivalences);

src/test/java/org/apache/sysds/test/component/codegen/rewrite/functions/SubtreeGeneratorTest.java

@@ -0,0 +1,48 @@
+package org.apache.sysds.test.component.codegen.rewrite.functions;
+
+import org.apache.sysds.hops.rewriter.RewriterStatement;
+import org.apache.sysds.hops.rewriter.RewriterUtils;
+import org.apache.sysds.hops.rewriter.RuleContext;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.List;
+import java.util.function.Function;
+
+public class SubtreeGeneratorTest {
+
+	private static RuleContext ctx;
+	private static Function<RewriterStatement, RewriterStatement> canonicalConverter;
+
+	@BeforeClass
+	public static void setup() {
+		ctx = RewriterUtils.buildDefaultContext();
+		canonicalConverter = RewriterUtils.buildCanonicalFormConverter(ctx, true);
+	}
+
+	@Test
+	public void test1() {
+		RewriterStatement stmt = RewriterUtils.parse("+(1, a)", ctx, "LITERAL_INT:1", "FLOAT:a");
+		List<RewriterStatement> subtrees = RewriterUtils.generateSubtrees(stmt, ctx, 100);
+
+		for (RewriterStatement sub : subtrees) {
+			System.out.println("==========");
+			System.out.println(sub.toParsableString(ctx, true));
+		}
+
+		assert subtrees.size() == 2;
+	}
+
+	@Test
+	public void test2() {
+		RewriterStatement stmt = RewriterUtils.parse("+(+(1, b), a)", ctx, "LITERAL_INT:1", "FLOAT:a,b");
+		List<RewriterStatement> subtrees = RewriterUtils.generateSubtrees(stmt, ctx, 100);
+
+		for (RewriterStatement sub : subtrees) {
+			System.out.println("==========");
+			System.out.println(sub.toParsableString(ctx, true));
+		}
+
+		assert subtrees.size() == 3;
+	}
+}