diff --git a/giraph-block-app-8/src/main/java/org/apache/giraph/block_app/library/triangles/UndirectedTriangleCountingBlockFactory.java b/giraph-block-app-8/src/main/java/org/apache/giraph/block_app/library/triangles/UndirectedTriangleCountingBlockFactory.java
new file mode 100644
index 0000000..90360d6
--- /dev/null
+++ b/giraph-block-app-8/src/main/java/org/apache/giraph/block_app/library/triangles/UndirectedTriangleCountingBlockFactory.java
@@ -0,0 +1,157 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.giraph.block_app.library.triangles;
+
+import org.apache.giraph.block_app.framework.AbstractBlockFactory;
+import org.apache.giraph.block_app.framework.api.BlockWorkerReceiveApi;
+import org.apache.giraph.block_app.framework.api.BlockWorkerSendApi;
+import org.apache.giraph.block_app.framework.block.Block;
+import org.apache.giraph.block_app.framework.block.IfBlock;
+import org.apache.giraph.block_app.framework.block.SequenceBlock;
+import org.apache.giraph.block_app.framework.piece.Piece;
+import org.apache.giraph.block_app.framework.piece.interfaces.VertexReceiver;
+import org.apache.giraph.block_app.framework.piece.interfaces.VertexSender;
+import org.apache.giraph.block_app.library.prepare_graph.PrepareGraphPieces;
+import org.apache.giraph.comm.messages.MessageEncodeAndStoreType;
+import org.apache.giraph.conf.BooleanConfOption;
+import org.apache.giraph.conf.GiraphConfiguration;
+import org.apache.giraph.conf.GiraphConstants;
+import org.apache.giraph.edge.Edge;
+import org.apache.giraph.edge.LongNullHashSetEdges;
+import org.apache.giraph.types.ops.LongTypeOps;
+import org.apache.giraph.types.ops.collections.array.WLongArrayList;
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.io.NullWritable;
+import org.apache.hadoop.io.Writable;
+import org.apache.hadoop.io.WritableComparable;
+
+import com.google.common.base.Preconditions;
+
+import it.unimi.dsi.fastutil.longs.LongListIterator;
+
+/**
+ * Count triangles in undirected graph.
+ * Assumes that edges in both directions are present, or optionally makes
+ * graph symmetric first.
+ */
+public class UndirectedTriangleCountingBlockFactory
+    extends AbstractBlockFactory<Object> {
+  /**
+   * Set to true to make graph symmetric before calculation if it's not already
+   */
+  public static final BooleanConfOption MAKE_GRAPH_SYMMETRIC =
+      new BooleanConfOption("giraph.triangleCounting.makeGraphSymmetric",
+          false, "Whether it's needed to first make graph symmetric or not");
+
+  @Override
+  protected Class<? extends WritableComparable> getVertexIDClass(
+      GiraphConfiguration conf) {
+    return LongWritable.class;
+  }
+
+  @Override
+  protected Class<? extends Writable> getVertexValueClass(
+      GiraphConfiguration conf) {
+    return LongWritable.class;
+  }
+
+  @Override
+  protected Class<? extends Writable> getEdgeValueClass(
+      GiraphConfiguration conf) {
+    return NullWritable.class;
+  }
+
+  @Override
+  public Block createBlock(GiraphConfiguration conf) {
+    return new SequenceBlock(
+        new IfBlock(() -> MAKE_GRAPH_SYMMETRIC.get(conf),
+            PrepareGraphPieces.makeSymmetricUnweighted(LongTypeOps.INSTANCE)),
+        new UndirectedCountTrianglesPiece());
+  }
+
+  @Override
+  public Object createExecutionStage(GiraphConfiguration conf) {
+    return new Object();
+  }
+
+  @Override
+  protected void additionalInitConfig(GiraphConfiguration conf) {
+    conf.setOutEdgesClass(LongNullHashSetEdges.class);
+    GiraphConstants.MESSAGE_ENCODE_AND_STORE_TYPE.setIfUnset(
+        conf, MessageEncodeAndStoreType.POINTER_LIST_PER_VERTEX);
+  }
+
+  /**
+   * Piece in which all vertices will send to their neighbors the list of their
+   * neighbors and vertices will count how many of received ids are their
+   * neighbors.
+   * TODO could be striped to make memory requirements lower
+   */
+  public static class UndirectedCountTrianglesPiece extends
+      Piece<LongWritable, LongWritable, NullWritable, WLongArrayList, Object> {
+    @Override
+    public VertexSender<LongWritable, LongWritable, NullWritable>
+    getVertexSender(
+        BlockWorkerSendApi<LongWritable, LongWritable, NullWritable,
+            WLongArrayList> workerApi,
+        Object executionStage) {
+      WLongArrayList reusableMessage = new WLongArrayList();
+      return vertex -> {
+        reusableMessage.clear();
+        for (Edge<LongWritable, NullWritable> edge : vertex.getEdges()) {
+          // TODO We could only send edge once
+          reusableMessage.add(edge.getTargetVertexId().get());
+        }
+        workerApi.sendMessageToAllEdges(vertex, reusableMessage);
+      };
+    }
+
+    @Override
+    public VertexReceiver<LongWritable, LongWritable, NullWritable,
+        WLongArrayList> getVertexReceiver(
+        BlockWorkerReceiveApi<LongWritable> workerApi, Object executionStage) {
+      LongWritable reusableId = new LongWritable();
+      return (vertex, messages) -> {
+        long numTriangles = 0;
+        for (WLongArrayList message : messages) {
+          LongListIterator iter = message.iterator();
+          while (iter.hasNext()) {
+            reusableId.set(iter.nextLong());
+            if (reusableId.get() != vertex.getId().get() &&
+                vertex.getEdgeValue(reusableId) != null) {
+              numTriangles++;
+            }
+          }
+        }
+        Preconditions.checkArgument(numTriangles % 2 == 0);
+        vertex.getValue().set(numTriangles / 2);
+      };
+    }
+
+    @Override
+    protected Class<WLongArrayList> getMessageClass() {
+      return WLongArrayList.class;
+    }
+
+    @Override
+    protected boolean allowOneMessageToManyIdsEncoding() {
+      return true;
+    }
+  }
+}
diff --git a/giraph-block-app-8/src/main/java/org/apache/giraph/block_app/library/triangles/package-info.java b/giraph-block-app-8/src/main/java/org/apache/giraph/block_app/library/triangles/package-info.java
new file mode 100644
index 0000000..330a384
--- /dev/null
+++ b/giraph-block-app-8/src/main/java/org/apache/giraph/block_app/library/triangles/package-info.java
@@ -0,0 +1,21 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+/**
+ * Triangle counting app
+ */
+package org.apache.giraph.block_app.library.triangles;
diff --git a/giraph-block-app-8/src/test/java/org/apache/giraph/block_app/library/triangles/TestUndirectedTriangleCounting.java b/giraph-block-app-8/src/test/java/org/apache/giraph/block_app/library/triangles/TestUndirectedTriangleCounting.java
new file mode 100644
index 0000000..5570c6c
--- /dev/null
+++ b/giraph-block-app-8/src/test/java/org/apache/giraph/block_app/library/triangles/TestUndirectedTriangleCounting.java
@@ -0,0 +1,82 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.giraph.block_app.library.triangles;
+
+import org.apache.giraph.block_app.framework.BlockUtils;
+import org.apache.giraph.block_app.framework.api.local.LocalBlockRunner;
+import org.apache.giraph.block_app.test_setup.NumericTestGraph;
+import org.apache.giraph.conf.GiraphConfiguration;
+import org.apache.hadoop.io.LongWritable;
+import org.apache.hadoop.io.NullWritable;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Test for {@link UndirectedTriangleCountingBlockFactory}
+ */
+public class TestUndirectedTriangleCounting {
+  @Test
+  public void smallTest() throws Exception {
+    GiraphConfiguration conf = new GiraphConfiguration();
+    BlockUtils.setAndInitBlockFactoryClass(
+        conf, UndirectedTriangleCountingBlockFactory.class);
+    NumericTestGraph<LongWritable, LongWritable, NullWritable> graph =
+        new NumericTestGraph<>(conf);
+
+    graph.addSymmetricEdge(1, 4);
+    graph.addSymmetricEdge(1, 5);
+    graph.addSymmetricEdge(1, 6);
+    graph.addSymmetricEdge(2, 4);
+    graph.addSymmetricEdge(2, 6);
+    graph.addSymmetricEdge(3, 6);
+    graph.addSymmetricEdge(4, 5);
+    graph.addSymmetricEdge(5, 6);
+
+    graph.addSymmetricEdge(7, 8);
+    graph.addSymmetricEdge(7, 9);
+    graph.addSymmetricEdge(8, 9);
+
+    graph.addSymmetricEdge(10, 11);
+    graph.addSymmetricEdge(10, 12);
+    graph.addSymmetricEdge(10, 13);
+    graph.addSymmetricEdge(10, 14);
+    graph.addSymmetricEdge(11, 12);
+    graph.addSymmetricEdge(11, 13);
+    graph.addSymmetricEdge(12, 13);
+    graph.addSymmetricEdge(13, 14);
+
+    LocalBlockRunner.runApp(graph.getTestGraph());
+
+    assertEquals(graph.getValue(1).get(), 2);
+    assertEquals(graph.getValue(2).get(), 0);
+    assertEquals(graph.getValue(3).get(), 0);
+    assertEquals(graph.getValue(4).get(), 1);
+    assertEquals(graph.getValue(5).get(), 2);
+    assertEquals(graph.getValue(6).get(), 1);
+    assertEquals(graph.getValue(7).get(), 1);
+    assertEquals(graph.getValue(8).get(), 1);
+    assertEquals(graph.getValue(9).get(), 1);
+    assertEquals(graph.getValue(10).get(), 4);
+    assertEquals(graph.getValue(11).get(), 3);
+    assertEquals(graph.getValue(12).get(), 3);
+    assertEquals(graph.getValue(13).get(), 4);
+    assertEquals(graph.getValue(14).get(), 1);
+  }
+}