[GitHub] [kafka] mjsax commented on a diff in pull request #13996: KAFKA-15022: [2/N] introduce graph to compute min cost
mjsax commented on code in PR #13996:
URL: https://github.com/apache/kafka/pull/13996#discussion_r1261835084
##
streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/Graph.java:
##
@@ -0,0 +1,363 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+public class Graph> {
+public class Edge implements Comparable {
+final V destination;
+final int capacity;
+final int cost;
+int residualFlow;
+int flow;
+Edge counterEdge;
+
+public Edge(final V destination, final int capacity, final int cost,
final int residualFlow, final int flow) {
+Objects.requireNonNull(destination);
+this.destination = destination;
+this.capacity = capacity;
+this.cost = cost;
+this.residualFlow = residualFlow;
+this.flow = flow;
+}
+
+@Override
+public int compareTo(final Edge o) {
Review Comment:
`compareTo` is to establish an order, right? Why do we order by
`(destination,capacity,cost)`; does is matter, or could we use any order as
long as deterministic?
##
streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/Graph.java:
##
@@ -0,0 +1,363 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+public class Graph> {
+public class Edge implements Comparable {
+final V destination;
+final int capacity;
+final int cost;
+int residualFlow;
+int flow;
+Edge counterEdge;
+
+public Edge(final V destination, final int capacity, final int cost,
final int residualFlow, final int flow) {
+Objects.requireNonNull(destination);
+this.destination = destination;
+this.capacity = capacity;
+this.cost = cost;
+this.residualFlow = residualFlow;
+this.flow = flow;
+}
+
+@Override
+public int compareTo(final Edge o) {
+int compare = destination.compareTo(o.destination);
+if (compare != 0) {
+return compare;
+}
+
+compare = capacity - o.capacity;
+if (compare != 0) {
+return compare;
+}
+
+return cost - o.cost;
+}
+
+@Override
+public boolean equals(final Object other) {
+if (this == other) {
+return true;
+}
+if (other == null || other.getClass() != getClass()) {
+return false;
+}
+
+final Graph.Edge otherEdge = (Graph.Edge) other;
+
+return destination.equals(otherEdge.destination) && capacity ==
otherEdge.capacity
+
[GitHub] [kafka] mjsax commented on a diff in pull request #13996: KAFKA-15022: [2/N] introduce graph to compute min cost
mjsax commented on code in PR #13996:
URL: https://github.com/apache/kafka/pull/13996#discussion_r1262977617
##
streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/Graph.java:
##
@@ -0,0 +1,348 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+public class Graph> {
+public class Edge {
+final V destination;
+final int capacity;
+final int cost;
+int residualFlow;
+int flow;
+Edge counterEdge;
+
+public Edge(final V destination, final int capacity, final int cost,
final int residualFlow, final int flow) {
+Objects.requireNonNull(destination);
+if (capacity < 0) {
+throw new IllegalArgumentException("Edge capacity cannot be
negative");
+}
+if (flow > capacity) {
+throw new IllegalArgumentException(String.format("Edge flow %d
cannot exceed capacity %d",
+flow, capacity));
+}
+
+this.destination = destination;
+this.capacity = capacity;
+this.cost = cost;
+this.residualFlow = residualFlow;
+this.flow = flow;
+}
+
+@Override
+public boolean equals(final Object other) {
+if (this == other) {
+return true;
+}
+if (other == null || other.getClass() != getClass()) {
+return false;
+}
+
+final Graph.Edge otherEdge = (Graph.Edge) other;
+
+return destination.equals(otherEdge.destination) && capacity ==
otherEdge.capacity
+&& cost == otherEdge.cost && residualFlow ==
otherEdge.residualFlow && flow == otherEdge.flow;
+}
+
+@Override
+public int hashCode() {
+return Objects.hash(destination, capacity, cost, residualFlow,
flow);
+}
+
+@Override
+public String toString() {
+return "{destination= " + destination + ", capacity=" + capacity +
", cost=" + cost
++ ", residualFlow=" + residualFlow + ", flow=" + flow;
+}
+}
+
+private final SortedMap> adjList = new TreeMap<>();
+private final SortedSet nodes = new TreeSet<>();
+private final boolean isResidualGraph;
+private V sourceNode, sinkNode;
+
+public Graph() {
+this(false);
+}
+
+private Graph(final boolean isResidualGraph) {
+this.isResidualGraph = isResidualGraph;
+}
+
+public void addEdge(final V u, final V v, final int capacity, final int
cost, final int flow) {
+addEdge(u, new Edge(v, capacity, cost, capacity - flow, flow));
+}
+
+public Set nodes() {
+return nodes;
+}
+
+public Map edges(final V node) {
+return adjList.get(node);
+}
+
+public boolean isResidualGraph() {
+return isResidualGraph;
+}
+
+public void setSourceNode(final V node) {
+sourceNode = node;
+}
+
+public void setSinkNode(final V node) {
+sinkNode = node;
+}
+
+public int totalCost() {
+int totalCost = 0;
+for (final Map.Entry> nodeEdges :
adjList.entrySet()) {
+final SortedMap edges = nodeEdges.getValue();
+for (final Entry nodeEdge : edges.entrySet()) {
+totalCost += nodeEdge.getValue().cost *
nodeEdge.getValue().flow;
+}
+}
+return totalCost;
+}
+
+private void addEdge(final V u, final Edge edge) {
+if (!isResidualGraph) {
+// Check if there's already an edge from u to v
+final Map edgeMap = adjList.get(edge.destination);
+if (edgeMap != null && edgeMap.containsKey(u)) {
+throw new IllegalArgumentException(
+"There is already an edge from " + edge.destination
+
[GitHub] [kafka] mjsax commented on a diff in pull request #13996: KAFKA-15022: [2/N] introduce graph to compute min cost
mjsax commented on code in PR #13996:
URL: https://github.com/apache/kafka/pull/13996#discussion_r1262978439
##
streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/Graph.java:
##
@@ -0,0 +1,348 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+public class Graph> {
+public class Edge {
+final V destination;
+final int capacity;
+final int cost;
+int residualFlow;
+int flow;
+Edge counterEdge;
+
+public Edge(final V destination, final int capacity, final int cost,
final int residualFlow, final int flow) {
+Objects.requireNonNull(destination);
+if (capacity < 0) {
+throw new IllegalArgumentException("Edge capacity cannot be
negative");
+}
+if (flow > capacity) {
+throw new IllegalArgumentException(String.format("Edge flow %d
cannot exceed capacity %d",
+flow, capacity));
+}
+
+this.destination = destination;
+this.capacity = capacity;
+this.cost = cost;
+this.residualFlow = residualFlow;
+this.flow = flow;
+}
+
+@Override
+public boolean equals(final Object other) {
+if (this == other) {
+return true;
+}
+if (other == null || other.getClass() != getClass()) {
+return false;
+}
+
+final Graph.Edge otherEdge = (Graph.Edge) other;
+
+return destination.equals(otherEdge.destination) && capacity ==
otherEdge.capacity
+&& cost == otherEdge.cost && residualFlow ==
otherEdge.residualFlow && flow == otherEdge.flow;
+}
+
+@Override
+public int hashCode() {
+return Objects.hash(destination, capacity, cost, residualFlow,
flow);
+}
+
+@Override
+public String toString() {
+return "{destination= " + destination + ", capacity=" + capacity +
", cost=" + cost
++ ", residualFlow=" + residualFlow + ", flow=" + flow;
+}
+}
+
+private final SortedMap> adjList = new TreeMap<>();
+private final SortedSet nodes = new TreeSet<>();
+private final boolean isResidualGraph;
+private V sourceNode, sinkNode;
+
+public Graph() {
+this(false);
+}
+
+private Graph(final boolean isResidualGraph) {
+this.isResidualGraph = isResidualGraph;
+}
+
+public void addEdge(final V u, final V v, final int capacity, final int
cost, final int flow) {
+addEdge(u, new Edge(v, capacity, cost, capacity - flow, flow));
+}
+
+public Set nodes() {
+return nodes;
+}
+
+public Map edges(final V node) {
+return adjList.get(node);
+}
+
+public boolean isResidualGraph() {
+return isResidualGraph;
+}
+
+public void setSourceNode(final V node) {
+sourceNode = node;
+}
+
+public void setSinkNode(final V node) {
+sinkNode = node;
+}
+
+public int totalCost() {
+int totalCost = 0;
+for (final Map.Entry> nodeEdges :
adjList.entrySet()) {
+final SortedMap edges = nodeEdges.getValue();
+for (final Entry nodeEdge : edges.entrySet()) {
+totalCost += nodeEdge.getValue().cost *
nodeEdge.getValue().flow;
+}
+}
+return totalCost;
+}
+
+private void addEdge(final V u, final Edge edge) {
+if (!isResidualGraph) {
+// Check if there's already an edge from u to v
+final Map edgeMap = adjList.get(edge.destination);
+if (edgeMap != null && edgeMap.containsKey(u)) {
+throw new IllegalArgumentException(
+"There is already an edge from " + edge.destination
+
[GitHub] [kafka] mjsax commented on a diff in pull request #13996: KAFKA-15022: [2/N] introduce graph to compute min cost
mjsax commented on code in PR #13996:
URL: https://github.com/apache/kafka/pull/13996#discussion_r1265999671
##
streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/Graph.java:
##
@@ -0,0 +1,367 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+public class Graph> {
+public class Edge {
+final V destination;
+final int capacity;
+final int cost;
+int residualFlow;
+int flow;
+Edge counterEdge;
+boolean forwardEdge;
+
+public Edge(final V destination, final int capacity, final int cost,
final int residualFlow, final int flow) {
+this(destination, capacity, cost, residualFlow, flow, true);
+}
+
+public Edge(final V destination, final int capacity, final int cost,
final int residualFlow, final int flow,
+final boolean forwardEdge) {
Review Comment:
nit: formatting (if it does not fit in one line, we should move each
parameter into it's one line to simplify reading)
```
public Edge(
final V destination,
final int capacity,
final int cost,
final int residualFlow,
final int flow,
final boolean forwardEdge
) {
```
##
streams/src/test/java/org/apache/kafka/streams/processor/internals/assignment/GraphTest.java:
##
@@ -0,0 +1,414 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.contains;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import org.junit.Before;
+import org.junit.Test;
+
+public class GraphTest {
+private Graph graph;
+
+@Before
+public void setUp() {
+/*
+ * Node 0 and 2 are both connected to node 1 and 3. There's a flow of
1 unit from 0 to 1 and 2 to
+ * 3. The total cost in this case is 5. Min cost should be 2 by
flowing 1 unit from 0 to 3 and 2
+ * to 1
+ */
+graph = new Graph<>();
+graph.addEdge(0, 1, 1, 3, 1);
+graph.addEdge(0, 3, 1, 1, 0);
+graph.addEdge(2, 1, 1, 1, 0);
+graph.addEdge(2, 3, 1, 2, 1);
+graph.addEdge(4, 0, 1, 0, 1);
+graph.addEdge(4, 2, 1, 0, 1);
+graph.addEdge(1, 5, 1, 0, 1);
+graph.addEdge(3, 5, 1, 0, 1);
+graph.setSourceNode(4);
+graph.setSinkNode(5);
+}
+
+@Test
+public void testBasic() {
+final Set nodes = graph.nodes();
+assertEquals(6, nodes.size());
+assertThat(nodes, contains(0, 1, 2, 3, 4, 5));
+
+Map.Edge> edges
[GitHub] [kafka] mjsax commented on a diff in pull request #13996: KAFKA-15022: [2/N] introduce graph to compute min cost
mjsax commented on code in PR #13996:
URL: https://github.com/apache/kafka/pull/13996#discussion_r1270057798
##
streams/src/test/java/org/apache/kafka/streams/processor/internals/assignment/GraphTest.java:
##
@@ -0,0 +1,414 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.contains;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import org.junit.Before;
+import org.junit.Test;
+
+public class GraphTest {
+private Graph graph;
+
+@Before
+public void setUp() {
+/*
+ * Node 0 and 2 are both connected to node 1 and 3. There's a flow of
1 unit from 0 to 1 and 2 to
+ * 3. The total cost in this case is 5. Min cost should be 2 by
flowing 1 unit from 0 to 3 and 2
+ * to 1
+ */
+graph = new Graph<>();
+graph.addEdge(0, 1, 1, 3, 1);
+graph.addEdge(0, 3, 1, 1, 0);
+graph.addEdge(2, 1, 1, 1, 0);
+graph.addEdge(2, 3, 1, 2, 1);
+graph.addEdge(4, 0, 1, 0, 1);
+graph.addEdge(4, 2, 1, 0, 1);
+graph.addEdge(1, 5, 1, 0, 1);
+graph.addEdge(3, 5, 1, 0, 1);
+graph.setSourceNode(4);
Review Comment:
Would it be simpler to use `0` as source? (At least for my mind it's easier
to follow what going on, if numbers are "ordered")
Or to avoid a lot of re-writing, name the source -1 (and the sink 99) so
both a clearly different, and we don't need to update too much code.
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[GitHub] [kafka] mjsax commented on a diff in pull request #13996: KAFKA-15022: [2/N] introduce graph to compute min cost
mjsax commented on code in PR #13996:
URL: https://github.com/apache/kafka/pull/13996#discussion_r1271147536
##
streams/src/main/java/org/apache/kafka/streams/processor/internals/assignment/Graph.java:
##
@@ -0,0 +1,377 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.SortedSet;
+import java.util.TreeMap;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
+
+public class Graph> {
+public class Edge {
+final V destination;
+final int capacity;
+final int cost;
+int residualFlow;
Review Comment:
Ah. Parameter order... Thought it's `, flow, residualFlow,` (not sure why
you picked the "reverse" order)
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[GitHub] [kafka] mjsax commented on a diff in pull request #13996: KAFKA-15022: [2/N] introduce graph to compute min cost
mjsax commented on code in PR #13996:
URL: https://github.com/apache/kafka/pull/13996#discussion_r1271148006
##
streams/src/test/java/org/apache/kafka/streams/processor/internals/assignment/GraphTest.java:
##
@@ -0,0 +1,414 @@
+/*
+ * 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.kafka.streams.processor.internals.assignment;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.contains;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import org.junit.Before;
+import org.junit.Test;
+
+public class GraphTest {
+private Graph graph;
+
+@Before
+public void setUp() {
+/*
+ * Node 0 and 2 are both connected to node 1 and 3. There's a flow of
1 unit from 0 to 1 and 2 to
+ * 3. The total cost in this case is 5. Min cost should be 2 by
flowing 1 unit from 0 to 3 and 2
+ * to 1
+ */
+graph = new Graph<>();
+graph.addEdge(0, 1, 1, 3, 1);
+graph.addEdge(0, 3, 1, 1, 0);
+graph.addEdge(2, 1, 1, 1, 0);
+graph.addEdge(2, 3, 1, 2, 1);
+graph.addEdge(4, 0, 1, 0, 1);
+graph.addEdge(4, 2, 1, 0, 1);
+graph.addEdge(1, 5, 1, 0, 1);
+graph.addEdge(3, 5, 1, 0, 1);
+graph.setSourceNode(4);
+graph.setSinkNode(5);
+}
+
+@Test
+public void testBasic() {
+final Set nodes = graph.nodes();
+assertEquals(6, nodes.size());
+assertThat(nodes, contains(0, 1, 2, 3, 4, 5));
+
+Map.Edge> edges = graph.edges(0);
+assertEquals(2, edges.size());
+assertEquals(getEdge(1, 1, 3, 0, 1), edges.get(1));
+assertEquals(getEdge(3, 1, 1, 1, 0), edges.get(3));
+
+edges = graph.edges(2);
+assertEquals(2, edges.size());
+assertEquals(getEdge(1, 1, 1, 1, 0), edges.get(1));
+assertEquals(getEdge(3, 1, 2, 0, 1), edges.get(3));
+
+edges = graph.edges(1);
+assertEquals(1, edges.size());
+assertEquals(getEdge(5, 1, 0, 0, 1), edges.get(5));
+
+edges = graph.edges(3);
+assertEquals(1, edges.size());
+assertEquals(getEdge(5, 1, 0, 0, 1), edges.get(5));
+
+edges = graph.edges(4);
+assertEquals(2, edges.size());
+assertEquals(getEdge(0, 1, 0, 0, 1), edges.get(0));
+assertEquals(getEdge(2, 1, 0, 0, 1), edges.get(2));
+
+edges = graph.edges(5);
+assertNull(edges);
+
+assertFalse(graph.isResidualGraph());
+}
+
+@Test
+public void testResidualGraph() {
+final Graph residualGraph = graph.residualGraph();
+final Graph residualGraph1 = residualGraph.residualGraph();
+assertSame(residualGraph1, residualGraph);
+
+final Set nodes = residualGraph.nodes();
+assertEquals(6, nodes.size());
+assertThat(nodes, contains(0, 1, 2, 3, 4, 5));
+
+Map.Edge> edges = residualGraph.edges(0);
+assertEquals(3, edges.size());
+assertEquals(getEdge(1, 1, 3, 0, 1), edges.get(1));
+assertEquals(getEdge(3, 1, 1, 1, 0), edges.get(3));
+assertEquals(getEdge(4, 1, 0, 1, 0, false), edges.get(4));
+
+edges = residualGraph.edges(2);
+assertEquals(3, edges.size());
+assertEquals(getEdge(1, 1, 1, 1, 0), edges.get(1));
+assertEquals(getEdge(3, 1, 2, 0, 1), edges.get(3));
+assertEquals(getEdge(4, 1, 0, 1, 0, false), edges.get(4));
+
+edges = residualGraph.edges(1);
+assertEquals(3, edges.size());
+assertEquals(getEdge(0, 1, -3, 1, 0, false), edges.get(0));
+assertEquals(getEdge(2, 1, -1, 0, 0, false), edges.get(2));
+assertEquals(getEdge(5, 1, 0, 0, 1), edges.get(5));
+
+edges = residualGraph.edges(3);
+assertEq
