diff --git a/src/test/java/org/apache/sysds/test/component/compress/colgroup/ColGroupTest.java b/src/test/java/org/apache/sysds/test/component/compress/colgroup/ColGroupTest.java
index 4c5fc3bd8a7..71c9c0ce549 100644
--- a/src/test/java/org/apache/sysds/test/component/compress/colgroup/ColGroupTest.java
+++ b/src/test/java/org/apache/sysds/test/component/compress/colgroup/ColGroupTest.java
@@ -29,6 +29,8 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Random;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.lang3.NotImplementedException;
 import org.apache.commons.logging.Log;
@@ -92,6 +94,9 @@
 public class ColGroupTest extends ColGroupBase {
 	protected static final Log LOG = LogFactory.getLog(ColGroupTest.class.getName());
 
+	/** Tracks already-logged "not implemented" column group type pairs to avoid duplicate log spam. */
+	private static final Set<String> loggedNotImplemented = ConcurrentHashMap.newKeySet();
+
 	public ColGroupTest(AColGroup base, AColGroup other, int nRow) {
 		super(base, other, nRow);
 	}
@@ -1282,7 +1287,7 @@ public void leftMultNoPreAgg(int nRowLeft, int rl, int ru, int cl, int cu, Matri
 			compare(bt, ot);
 		}
 		catch(NotImplementedException e) {
-			LOG.error("not implemented: " + base.getClass().getSimpleName() + " or: " + other.getClass().getSimpleName());
+			logNotImplementedOnce();
 		}
 		catch(Exception e) {
 			e.printStackTrace();
@@ -1290,6 +1295,12 @@ public void leftMultNoPreAgg(int nRowLeft, int rl, int ru, int cl, int cu, Matri
 		}
 	}
 
+	private void logNotImplementedOnce() {
+		final String pair = base.getClass().getSimpleName() + " or: " + other.getClass().getSimpleName();
+		if(loggedNotImplemented.add(pair))
+			LOG.error("not implemented: " + pair);
+	}
+
 	@Test
 	public void sparseSelection() {
 		MatrixBlock mb = CLALibSelectionMultTest.createSelectionMatrix(nRow, 5, false);