Updated the FlowEngine so nodes that have to be updated in the current cycle cannot be scheduled twice. (#284)

Updated the FlowNodeQueue

3 files changed, 37 insertions, 27 deletions

diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/engine/FlowNodeQueue.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/engine/FlowCycleQueue.java
index bd622083..72dd217c 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/engine/FlowNodeQueue.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/engine/FlowCycleQueue.java
@@ -28,28 +28,32 @@ import org.opendc.simulator.engine.graph.FlowNode;
 
 /**
  * A specialized {@link ArrayDeque} implementation that contains the {@link FlowNode}s
- * that have been updated during the engine cycle and should converge.
+ * that should be updated in the current cycle, because of a change caused by another update in the current cycle.
  * <p>
  * By using a specialized class, we reduce the overhead caused by type-erasure.
  */
-final class FlowNodeQueue {
+final class FlowCycleQueue {
     /**
      * The array of elements in the queue.
      */
-    private FlowNode[] elements;
+    private FlowNode[] nodeQueue;
 
     private int head = 0;
     private int tail = 0;
 
-    public FlowNodeQueue(int initialCapacity) {
-        elements = new FlowNode[initialCapacity];
+    public FlowCycleQueue(int initialCapacity) {
+        nodeQueue = new FlowNode[initialCapacity];
     }
 
     /**
      * Add the specified context to the queue.
      */
     void add(FlowNode ctx) {
-        final FlowNode[] es = elements;
+        if (ctx.getInCycleQueue()) {
+            return;
+        }
+
+        final FlowNode[] es = nodeQueue;
         int tail = this.tail;
 
         es[tail] = ctx;
@@ -60,19 +64,22 @@ final class FlowNodeQueue {
         if (head == tail) {
             doubleCapacity();
         }
+
+        ctx.setInCycleQueue(true);
     }
 
     /**
      * Remove a {@link FlowNode} from the queue or <code>null</code> if the queue is empty.
      */
     FlowNode poll() {
-        final FlowNode[] es = elements;
+        final FlowNode[] es = nodeQueue;
         int head = this.head;
         FlowNode ctx = es[head];
 
         if (ctx != null) {
             es[head] = null;
             this.head = inc(head, es.length);
+            ctx.setInCycleQueue(false);
         }
 
         return ctx;
@@ -82,13 +89,13 @@ final class FlowNodeQueue {
      * Doubles the capacity of this deque
      */
     private void doubleCapacity() {
-        int oldCapacity = elements.length;
+        int oldCapacity = nodeQueue.length;
         int newCapacity = oldCapacity + (oldCapacity >> 1);
         if (newCapacity < 0) {
             throw new IllegalStateException("Sorry, deque too big");
         }
 
-        final FlowNode[] es = elements = Arrays.copyOf(elements, newCapacity);
+        final FlowNode[] es = nodeQueue = Arrays.copyOf(nodeQueue, newCapacity);
 
         // Exceptionally, here tail == head needs to be disambiguated
         if (tail < head || (tail == head && es[head] != null)) {
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/engine/FlowEngine.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/engine/FlowEngine.java
index 1a068b40..24476048 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/engine/FlowEngine.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/engine/FlowEngine.java
@@ -37,9 +37,9 @@ import org.opendc.simulator.engine.graph.FlowNode;
  */
 public final class FlowEngine implements Runnable {
     /**
-     * The queue of {@link FlowNode} updates that are scheduled for immediate execution.
+     * The queue of {@link FlowNode} updates that need to be updated in the current cycle.
      */
-    private final FlowNodeQueue queue = new FlowNodeQueue(256);
+    private final FlowCycleQueue cycleQueue = new FlowCycleQueue(256);
 
     /**
      * A priority queue containing the {@link FlowNode} updates to be scheduled in the future.
@@ -112,7 +112,7 @@ public final class FlowEngine implements Runnable {
      * This method should only be invoked while inside an engine cycle.
      */
     public void scheduleImmediateInContext(FlowNode ctx) {
-        queue.add(ctx);
+        cycleQueue.add(ctx);
     }
 
     /**
@@ -147,7 +147,7 @@ public final class FlowEngine implements Runnable {
      * Run all the enqueued actions for the specified timestamp (<code>now</code>).
      */
     private void doRunEngine(long now) {
-        final FlowNodeQueue queue = this.queue;
+        final FlowCycleQueue queue = this.cycleQueue;
         final FlowTimerQueue timerQueue = this.timerQueue;
 
         try {
diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/graph/FlowNode.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/graph/FlowNode.java
index b2827130..64cd0d8c 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/graph/FlowNode.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/engine/graph/FlowNode.java
@@ -60,6 +60,14 @@ public abstract class FlowNode {
         this.timerIndex = index;
     }
 
+    public Boolean getInCycleQueue() {
+        return inCycleQueue;
+    }
+
+    public void setInCycleQueue(Boolean inCycleQueue) {
+        this.inCycleQueue = inCycleQueue;
+    }
+
     public InstantSource getClock() {
         return clock;
     }
@@ -105,6 +113,8 @@ public abstract class FlowNode {
      */
     private int timerIndex = -1;
 
+    private Boolean inCycleQueue = false;
+
     protected InstantSource clock;
     protected FlowGraph parentGraph;
     protected FlowEngine engine;
@@ -139,9 +149,9 @@ public abstract class FlowNode {
     public void invalidate(long now) {
         // If there is already an update running,
         // notify the update, that a next update should be run after
-        if (this.nodeState == NodeState.UPDATING) {
+
+        if (this.nodeState != NodeState.CLOSING && this.nodeState != NodeState.CLOSED) {
             this.nodeState = NodeState.INVALIDATED;
-        } else {
             engine.scheduleImmediate(now, this);
         }
     }
@@ -172,15 +182,16 @@ public abstract class FlowNode {
             doFail(e);
         }
 
-        // Check whether the stage is marked as closing.
-        if (this.nodeState == NodeState.INVALIDATED) {
-            newDeadline = now;
-        }
         if (this.nodeState == NodeState.CLOSING) {
             closeNode();
             return;
         }
 
+        // Check whether the stage is marked as closing.
+        if ((this.nodeState == NodeState.INVALIDATED) || (this.nodeState == NodeState.CLOSED)) {
+            return;
+        }
+
         this.deadline = newDeadline;
 
         // Update the timer queue with the new deadline
@@ -211,14 +222,6 @@ public abstract class FlowNode {
      */
     public void closeNode() {
         if (this.nodeState == NodeState.CLOSED) {
-            //            LOGGER.warn("Flowstage:doClose() => Tried closing a stage that was already closed");
-            return;
-        }
-
-        // If this stage is running an update, notify it that is should close after.
-        if (this.nodeState == NodeState.UPDATING) {
-            //            LOGGER.warn("Flowstage:doClose() => Tried closing a stage, but update was active");
-            this.nodeState = NodeState.CLOSING;
             return;
         }